UC-NRLF 


Lummor  Soxoo   Of  Ohomio 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

OIKT  OF^ 


/?    f  OIKT  OF* 


Accession  No.  (0*  Class  No. 


'  : 
&<i>i  FRANCISCO,  CAL» 


ELEMENTARY   CHEMISTRY 


BY 

GEORGE   RANTOUL   WHITE,  A.M. 

ii 

INSTRUCTOR  TN  CHEMISTRY  AT   PHILLIPS  EXETER  ACADEMY 


BOSTON,  U.S.A. 

PUBLISHED    BY   GINN   &   COMPANY 
1894 


COPYRIGHT,  1894 
BY  GEORGE  RANTOUL  WHITE 


ALL  RIGHTS  RESERVED 


PREFACE. 


THIS  book  is  little  more  than  a  reproduction  of  the 
course  in  elementary  chemistry  as  now  given  at  Exeter 
Academy.  The  course  itself  has  been  developed,  little 
by  little,  during  several  years  of  observation  and  experi- 
ment on  the  part  of  the  writer,  to  meet  the  needs  of  all 
classes  of  students,  —  those  who  are  preparing  for  a 
further  course  of  study  at  college,  those  who  expect  to 
enter  a  scientific  school,  and  those  who  go  from  the 
academy  directly  to  their  life-work.  The  majority  of 
all  these  students  take  chemistry  merely  as  a  part  of  a 
liberal  education,  some  intend  to  follow  the  paths  of 
science  ;  a  few  will  become  chemists. 

In  planning  this  work  for  beginners  the  writer  has 
tried  to  prepare  a  course  that  will  meet  the  needs  of 
one  class  as  well  as  those  of  another.  But  in  this 
respect  his  task  has  been  easy,  for  the  more  he  has 
considered  the  needs  of  the  various  classes,  the  more  he 
has  come  to  believe  that  the  elementary  training  of  all 
should  be  alike.  The  student  who  is  to  be  a  lawyer,  a 
doctor,  or  a  man  of  business,  needs  that  same  careful 
attention  to  details,  that  same  power  of  accurate  ob- 
servation which  is  expected  of  the  coming  chemist ; 
and  he  who  is  to  be  the  chemist  needs  the  same  high 
development  of  his  reasoning  powers  as  he  who  takes 
chemistry  only  for  the  intellectual  training  it  can  give. 


IV  PREFACE. 

This  book  is  designed  especially  for  the  use  of  two 
classes  of  students.  First  for  those  whose  instruction 
is  placed  in  the  hands  of  a  teacher  who  cannot  devote 
his  whole  time  to  chemistry  ;  and  secondly,  for  young 
men  and  women  who  are  eager  to  study  chemistry  but 
have  no  teacher  at  all. 

In  regard  to  the  first  class  —  those  instructed  by 
teachers  who  are  not  strictly  and  solely  teachers  of 
chemistry  —  the  writer  believes  that  it  is  not  possible 
for  any  teacher  to  get  the  best  results  from  his  students 
if  he  has  to  divide  his  attention,  his  energy,  his  love, 
between  two  or  more  subjects.  We  cannot  serve  two 
masters.  Those  students  who  are  so  fortunate  as  to 
have  an  instructor  who  can  devote  his  whole  time  to 
the  presentation  of  elementary  chemistry  need  no  book 
at  all.  The  instructor  will  himself  more  than  take  the 
place  of  a  book.  But  it  is  seldom  that  a  school  or  col- 
lege has  a  chemist  who  can  devote  his  whole  time  to 
developing  the  elementary  course.  Generally  the  in- 
structor in  chemistry  must  teach  some  other  study. 
Even  when  he  can  give  all  his  attention  to  chemistry, 
his  time  often  is  chiefly  devoted  to  the  more  advanced 
students.  Though  the  instructor  can  well  replace  the 
book,  no  book  can  fully  take  the  place  of  an  instructor. 
It  is  hoped,  however,  that  this  book  may  be  of  some 
service  in  supplementing  the  work  of  those  instructors 
who  have  not  the  time  to  do  for  their  pupils  all  that 
they  really  desire. 

To  those  students  who  can  never  have  any  instruc- 
tor, but  want  to  study  chemistry,  the  strictly  inductive 
method  here  followed  lends  itself  well.  There  are, 


PREFACE.  V 

moreover,  no  experiments  inserted  that  have  not  been 
well  tried,  and  found  to  work  successfully  in  the  hands 
of  beginners.  Wherever  there  seems  danger  —  and 
danger  there  must  be,  to  some  extent,  in  every  course  of 
chemistry  that  is  worth  the  giving  —  abundant  warning 
is  inserted.  Through  all  the  development  of  this  course 
at  Exeter  there  has  never  been  an  accident  at  all  serious. 

It  will  be  noted  by  him  who  looks  through  the  pages 
of  this  book,  first,  that  the  method  of  presenting  ele- 
mentary chemistry  here  embodied  is  preeminently  a 
practical  or  laboratory  method,  and,  secondly,  that  the 
method  is  preeminently  inductive. 

To-day  no  plea  for  the  laboratory  or  practical  method 
of  presenting  any  study  seems  needed.  As  James 
Russell  Lowell  has  said,  "  Practical  application  is  the 
only  mordant  which  will  set  things  in  the  memory. 
Study  without  it  is  gymnastics,  and  not  work,  which 
alone  will  get  intellectual  bread."  In  no  branch  of 
learning  does  the  laboratory  method  seem  more  essen- 
tial than  in  chemistry,  and  in  no  branch  has  this 
method  been  more  widely  adopted  than  in  chemistry. 
Everywhere  laboratories  are-  being  built,  and  nowhere, 
so  far  as  the  writer  has  ever  heard,  has  there  been  a 
change  back  to  the  old  method  after  the  new  has  once 
been  tried.  The  results,  however,  always  justify  the 
change  from  the  old  to  the  new.  Professor  Cooke, 
director  of  the  Chemical  Laboratory  at  Harvard  Uni- 
versity, where  for  years  chemistry  has  been  taught 
in  no  other  way  than  by  the  laboratory  method,  writes, 
"How  little  of  what  we  value  comes  to  us  by  the 
way  of  direct  teaching  !  There  may  be  such  a  thing 


vi  PREFACE. 

as  too  much  teaching,  and  even  —  in  spite  of  the 
paradox  —  too  good  teaching  ;  for,  after  all,  personal 
experience  is,  at  the  university  as  elsewhere,  the  most 
efficient  teacher,  and  he  who  encourages  us  to  help 
ourselves  is  our  safest  guide." 

In  working  out  the  course  indicated  in  this  book 
it  has  been  the  writer's  aim  to  make  this  "  personal  ex- 
perience "  for  the  student  as  large  as  possible.  He 
always  tells  his  Exeter  students  that  he  is  their  com- 
panion more  than  their  teacher ;  that  their  own  experi- 
ence, acquired  little  by  little,  through  hours  of  work  in 
the  laboratory,  must  be  their  true  teacher ;  while  he 
himself  simply  is  their  guide,  showing  where  the  path 
runs  smoothest,  warning  against  innumerable  by-paths, 
pleasant  to  follow  it  is  true,  but  that  lead  nowhere, 
pointing  out  the  dangers  to  be  avoided  and,  alas  !  not 
infrequently  having  to  point  out  the  beauties  that 
other  travelers  on  the  same  way  have  noted,  —  beauties 
that  would  otherwise  be  passed  by,  all  unheeded  by  the 
impetuosity  of  youth. 

At  first  the  student  is  told  little  or  nothing.  He  is 
compelled  to  find  out  all  things  for  himself.  To  assist 
him  in  finding  the  essential,  and  to  make  sure  that  he 
has  succeeded  in  this,  frequent  questions  are  inserted 
in  the  text  of  the  experimental  part.  [For  the  use  to 
be  made  of  these  questions,  see  Introduction.]  The 
author  believes  that  questions  inserted  thus,  just  at  the 
point  when  the  inquiry  naturally  springs  to  the  lips  of 
a  bright  student,  are  of  more  value  than  the  same  ques- 
tions inserted  all  together  at  the  end  of  a  book  or  even 
in  groups  at  the  end  of  the  chapters. 


tKEFACE.  vii 

There  is  a  marked  tendency  among  bright  students 
who  are  taking  up  a  new  subject  for  study,  to  ask 
questions.  This  tendency  can  readily  be  checked  by 
the  teacher's  refusing  to  answer  such  questions  and 
telling  the  pupils  to  confine  themselves  to  the  text  of 
the  book  ;  or  it  can  be  developed,  by  proper  training, 
into  one  of  the  highest  and  most  valuable  powers  of  the 
human  mind  —  logical  reasoning.  It  was  by  attempting 
to  win  something  of  good  from  this  asking  of  questions 
that  the  author  of  this  book  was  led  to  arrange  the 
work  of  his  elementary  class  on  a  strictly  inductive 
basis.  A  fresh  young  mind  is  very  loath  to  take  any- 
thing for  granted, — it  is  naturally  questioning.  To  be 
sure,  it  is  always  easy  to  destroy  this  natural  condition, 
and  to  accustom  a  pupil  to  have  implicit  faith  in  his 
teacher  ;  implicit  faith  in  his  book  ;  in  fact,  from  the 
very  method  by  which  we  have  most  of  us  been  taught, 
we  are  obliged  to  say,  if  questioned  as  to  our  reason  for 
believing  a  certain  statement,  that  we  believe  it  because 
so  and  so  has  told  us,  or  because  such  and  such  a  book 
says  so.  How  much  more  of  profit  and  pleasure  will 
come  to  a  future  generation  if  only  we  can  teach  the 
children  of  to-day  —  who  are  to  be  the  men  and  women 
of  to-morrow  —  to  think  and  to  reason  for  themselves. 
As  President  Eliot  of  Harvard  has  recently  said  :  "  The 
main  processes  or  operations  of  the  mind"  which  should 
be  developed  "  in  an  individual  in  order  to  increase  his 
general  intelligence  and  train  his  reasoning  power" 
are,  first,  "  observation,  that  is  to  say,  the  alert,  intent, 
and  accurate  use  of  his  senses";  next,  "the  function 
of  making  a  correct  record  of  things  observed";  next, 


Vlll  PREFACE. 

"  the  faculty  of  drawing  correct  inferences  from  recorded 
observations.  ...  It  is  often  a  long  way  from  the 
patent  fact  to  the  just  inference.  For  centuries  the 
Phoenician  and  Roman  navigators  had  seen  the  hulls 
of  vessels  disappearing  below  the  blue  horizon  of  the 
Mediterranean  while  their  sails  were  visible  ;  but  they 
never  drew  the  inference  that  the  earth  was  round." 

It  is  easier  to  learn  [?]  a  thing  from  a  book  or  from  a 
teacher  than  by  reasoning  it  out  for  ourselves.  But  do 
we  get  from  the  memorizing  process  the  results  that  are 
needed  for  an  education?  There  must  come  a  time 
when  almost  every  student  will  find  himself  in  a  great 
school  where  he  himself  is  not  pupil  but  master,  where 
there  are  no  books  to  which  he  can  refer.  Herbert 
Spencer,  speaking  of  the  state  of  education,  has  said  : 
"  Nearly  every  subject  dealt  with  is  arranged  in  abnor- 
mal order  ;  definitions,  and  rules,  and  principles  being 
put  first,  instead  of  being  disclosed,  as  they  are  in  the 
order  of  nature,  through  the  study  of  cases.  And  then 
pervading  the  whole  is  the  vicious  system  of  rote  learn- 
ing—  a  system  of  sacrificing  the  spirit  to  the  letter. 
See  the  results."  Though  there  have  been  marked 
changes  since  these  words  were  written,  some  thirty 
years  ago,  still  there  is  at  the  present  day  much  "  rote 
learning,"  even  among  chemical  students. 

As  an  instructor  for  several  summers  in  the  Harvard 
Summer  School  at  Cambridge  [where  teachers  from 
almost  all  parts  of  the  country  assemble],  the  writer  has 
had  an  opportunity  to  judge  of  the  methods  of  instruc- 
tion generally  employed,  and  to  "  see  the  results."  To 
him  the  results  have  not  seemed  satisfactory.  Those 


PREFACE.  IX 

taught  by  the  common  methods,  at  the  best,  have  a 
considerable  knowledge  of  facts,  and  sometimes  can 
make  a  few  simple  analyses,  but  they  seldom  have  the 
power  of  doing  any  thinking  for  themselves.  Believing, 
as  the  author  does,  that  there  is  no  other  study  which, 
pursued  for  either  one,  two,  or  three  years,  can  give  so 
much  in  return  that  is  of  an  educational  value,  he  has 
been  grieved  and  ashamed  to  realize  how  little  is 
obtained  by  the  many,  mostly  faithful,  students  of  that 
science.  Seeking  for  the  cause,  the  writer  has  come  to 
the  conclusion  that  it  lies  in  the  method  of  presenting 
the  subject.  It  is  seldom  that  a  pupil  knows  much  of 
anything  about  this  science  till  he  has  studied  it  four, 
five,  or  more  years.  Then  the  real  meaning  of  all  he 
has  been  working  over  gradually  dawns  upon  him. 
But  how  is  it  with  the  great  majority  of  one,  two,  and 
three  year  students  who,  never  intending  to  be 
chemists,  have  taken  up  the  study  only  as  a  part  of  a 
liberal  education  ?  Most  of  these  have  actually  wasted 
the  time  spent  on  their  chemistry.  The  trouble  is  that 
most  text-books  aim  at  giving  a  synopsis  of  the  whole 
of  chemistry.  The  writers  do  not  seem  to  realize  how 
vast  an  accumulation  of  facts  now  lie  open  to  the 
chemist :  that  to  try  to  learn  all  these  facts  is  as 
profitless  a  task  as  for  the  beginner  in  English  compo- 
sition to  start  by  learning  all  the  words  in  his  diction- 
ary. Is  it  not  better  for  both  to  confine  themselves  to 
a  little  that  is  of  everyday  occurrence  and  learn  that 
little  thoroughly?  Then  again,  to  the  writer,  it  seems 
that  the  text-books  for  beginners  err  in  being  "  arranged 
in  abnormal  order  :  definitions,  and  rules  and  principles 


X  PREFACE. 

being  put  first,  instead  of  being  disclosed,  as  they  are 
in  the  order  of  nature,  through  the  study  of  cases."  In 
the  following  pages  a  "  study  of  cases  "  comes  first.  In 
fact  for  some  time  the  pupil  does  nothing  but  study 
cases  ;  very  simple  ones  at  first  —  many,  though,  that 
have  been  familiar  to  him  all  his  life  ;  then  less  familiar 
and  more  complicated  ones  ;  and,  finally,  in  Ex.  32, 
"A  Chemical  Investigation,"  he  has  before  him  a 
problem  not  unlike  the  many  that  are  constantly  pre- 
sented to  the  chemist  who  is  working  on  the  border- 
land, of  the  science.  To  the  end  of  this  "  Chemical 
Investigation,"  the  whole  course  is  inductive.  It  is 
believed  that  not  an  essential  question  can  be  asked 
that  the  student  cannot  answer  either  from  observation 
of  the  phenomena  or  from  reasoning  based  on  previous 
experiment.  Through  the  whole  of  Part  I  the  student 
becomes  acquainted  with  the  methods  —  both  mental 
and  practical  —  of  the  scientific  chemist  of  to-day.  He 
learns  to  experiment,  to  observe,  to  reason.  He  accepts 
nothing  simply  because  his  teacher,  or  the  book,  says  it 
is  so.  Everything  he  verifies  by  himself  to  his  own 
satisfaction.  Then,  having  learned  by  many  experi- 
ments [particularly  by  "  A  Chemical  Investigation "] 
how  the  chemist  obtains  the  facts  that  are  at  the  basis 
of  all  his  reasoning,  the  student  is  prepared  to  trace  with 
pleasure  [in  Part  III]  the  history  of  chemistry,  to  note 
what  observations  lead  to  the  establishment  of  certain 
theories,  and  the  recognition  of  what  facts  lead  to  the 
overthrow  of  these  same  theories  ;  to  recognize  the 
gradual  unfolding  of  chemical  law ;  and,  finally,  to 
inspect  the  foundations  on  which  our  present  Atomic 


PREFACE.  XI 

Theory  rests,  and  have  an  opinion  of  his  own  as  to  its 
stability.  The  author  has  thought  best  to  give  a  more 
extended  account  of  the  development  of  the  laws  and 
theories  of  chemistry  than  is  usually  found  in  text- 
books. He  has  been  led  to  this  for  several  reasons  : 
first,  because  he  believes  that  every  educated  man  or 
woman  should  possess  a  knowledge  of  these  laws  and 
theories  ;  secondly,  because  he  feels  that  a  consideration 
of  their  development  gives  the  student  an  excellent 
introduction  to  the  true  spirit  of  scientific  investigation ; 
and,  finally,  because  he  is  well  aware  that  advanced 
students  of  chemistry  generally  lack  a  fundamental 
knowledge  of  the  history  and  development  of  their  own 
branch  of  science.  Text-books  for  beginners  usually 
omit  a  thorough  treatment  of  the  laws  and  theories  as 
beyond  their  scope,  while  the  .books  for  advanced 
students  also  omit  the  same  on  the  ground  that  the 
student  has  already  learned  the  fundamental  principles. 
Where,  then,  is  the  student  to  get  this  knowledge  ? 

It  may  also  be  noted  that  for  a  long  time  no  hint 
is  given  that  there  are  such  things  as  chemical  symbols. 
Not  to  accustom  the  pupils  from  the  first  to  express 
facts  in  the  language  of  chemistry,  will  doubtless  seem 
to  many  both  silly  and  wrong.  But  to  do  so  would 
not  be  in  accord  with  the  spirit  of  the  inductive 
method  here  employed.  When  the  student  has  mastered 
the  facts,  it  is  a  pleasure  to  see  how  readily  he  ex- 
presses those  facts  by  the  proper  symbols.  This  he 
then  does  accurately  and  almost  without  an  effort. 
The  writer  several  years  ago  adopted  the  plan  of 
having  his  students  express  the  facts  in  English  till 


Xll  PREFACE. 

enough  facts  had  been  collected  for  the  students  to  use 
the  language  of  chemistry  freely  and  accurately.  He 
has  no  desire  to  go  back  to  the  old  method.  Then, 
too,  when  symbols  are  used  before  they  can  be  fully 
understood,  there  is  danger  that  the  symbols,  and 
not  the  facts  they  express,  may  be  looked  at  as  the 
realities.  For  instance,  on  a  recent  [English]  examina- 
tion paper  there  appeared  the  following  :  "  Account 
for  the  basicity  of  phosphorus  and  hypophosphorus 
acids,  respectively,  by  reference  to  their  constitutional 
formulae."  At  the  best,  formulae  can  only  express  the 
facts  we  have  found  out  about  substances  ;  they  cannot 
account  for  any  of  these  facts,  and  the  student  should  not 
be  taught  that  they  can.  In  this  connection  it  may  be 
of  interest  to  note  the  following  taken  from  the  intro- 
duction to  the  first  edition  of  Meyer's  "  Moderne  Theo- 
rien  der  Chemie."  The  translation  reads,  "Chemical 
symbols  and  formulae,  which  a  few  years  ago  received 
such  prominence,  are  now  regarded  with  indifference, 
since  what  was  formerly  expressed  symbolically  and 
indistinctly  or  even  without  proof  or  clearness  by  their 
aid,  can  now  be  expressed  in  clear  words  with  fixed 
meaning."  And  again,  very  recently,  no  less  an  au- 
thority than  Professor  Remsen,  of  Johns  Hopkins 
University,  has  written  that  he  "  sometimes  thinks,  and 
the  intervals  between  the  thoughts  are  getting  shorter, 
that  if  the  use  of  formulae  were  given  up  entirely  in 
elementary  instruction,  better  results  would  be  ob- 
tained." 

FEBRUARY,  1894. 


COISTTEE'TS. 


PAGE 

INTRODUCTION xxiii 

PRELIMINARY  WORK 

Measuring 3 

Weighing 4 

Making  a  wash-bottle 6 

PART  I.     EXPERIMENTS. 
Ex.    1.  Iron 

A.  Properties 11 

B.  With  Air 11 

2.  Phosphorus 

A.  Properties 12 

B.  With  Air 13 

3.  Mercury 14 

4.  Carbon 14 

5.  Artificial  Preparation  of  Oxygen 

A.  From  Red  Oxide  of  Mercury 15 

B.  From  Chlorate  of  Potassium 16 

6.  Action  of  Undiluted  Oxygen  Gas 

A.  On  Iron 17 

B.  On  Phosphorus  18 

C.  On  Carbon 18 

7.  Preparation  of  Oxygen  from  Water 19 

8.  Examination  of  that  Constituent  of  Water  which  is 

not  Oxygen 20 

9.  Hydrogen 

A.  Preparation  from  Water  by  means  of  Iron 20 

B.  Specific  Gravity 22 

C.  Action  of  Air  on  Warm  Hydrogen 22 

10.  Sulphur 

A.  Properties 23 

B.  Modifications 24 

C.  Action  of  Oxygen  on  Hot  Sulphur 25 


XIV  CONTENTS. 

PAGE 

Ex.  11.  Sulphurous  Acid 27 

12.  A  Second  Oxide  of  Sulphur 27 

13.  Sulphuric  Acjd 29 

14.  Removal  of  Hydrogen  from  Sulphuric  Acid 30 

15.  Action  of  Water  on  Oxide  of  Iron 32 

16.  Action  of  Water  on  Oxide  of  Phosphorus 33 

17.  Action  of  Water  on  Oxide  of  Carbon 33 

18.  Zinc 

A.  Properties 34 

B.  Oxidation  of  Zinc 34 

C.  Action  of  Water  on  Oxide  of  Zinc 34 

19.  Action  of  Zinc  on  the  Non-combustible  Oxide  of 

Carbon ;  or, 

Preparation  of  a  Second  Oxide  of  Carbon 35 

20.  Oxidation  of  the  Combustible  Oxide  of  Carbon 37 

21.  Action  of  Zinc  on  Sulphuric  Acid 37 

22.  Action  of  Oxide  of  Zinc  on  Sulphuric  Acid 38 

23.  Sulphides 

A.  Mutual  Action  of  Iron  and  Sulphur 39 

B.  Action  of  Hydrogen  on  Warm  Sulphur 39 

O.  Action  of  Sulphuric  Acid  on  Sulphide  of  Iron..  40 

24.  Copper 

A.  Properties 41 

B.  Oxidation 41 

C.  Reduction  of  the  Black  Oxide 42 

25.  Magnesium 

A.  Properties 43 

B.  Oxidation 43 

C.  Magnesium  Oxide  -with  Water 43 

JD.  Magnesium  and  Sulphuric  Acid 43 

26.  Calcium 

A.  Properties 44 

B.  Oxidation 44 

C.  Reaction  of  Oxide  of  Calcium  and  Water 45 

D.  Action  of  Calcium  on  Water 45 

E.  Reaction   of  Hydrate  of  Calcium  and  Sul- 

phuric Acid 46, 

F.  Reaction  of  Hydrate  of  Calcium  and  Carbonic 

Acid ........ 


CON 


Ex.  26.  Calcium  PAGE 

G.  Analysis  of  Marble 50 

If.  Reaction  of  Marble  and  Sulphuric  Acid 51 

27.  Sodium 

A.  Properties 52 

B.  Oxidation 52 

C.  Reaction  of  Oxide  of  Sodium  and  Water 53 

D.  Action  of  Sodium  on  Water 63 

E.  Reaction  of  Sodium  Hydroxide  and  Sulphuric 

Acid 54 

F.  Reaction  of  Sodium  Hydroxide  and  Carbonic 

Acid 54 

G.  Reaction  of  Hydrate  of  Sodium  and  the  Non- 

combustible  Oxide  of  Carbon 55 

H.  Reaction  of  Carbonate  of  Sodium  and  Sul- 
phuric Acid 55 

/.  Reaction  of  Sodium  and  Mercury 55 

28.  Chlorine 56 

29.  Chlorides 

A.  Chloride  of  hydrogen 56 

B.  Chloride  of  Sodium 57 

C.  Preparation  of  Hydrochloric  Acid  on  a  Large 

Scale 57 

D.  Solubility  of  Hydrochloric  Acid 58 

E.  Reaction  of  Hydrochloric  Acid  and  Marble  ....  58 

F.  Action  of  Sodium  on  Hydrochloric  Acid 59 

G.  Action   of   Sodium   Hydroxide  with   Hydro- 

chloric Acid 60 

30.  Potassium 

A.  Properties  61 

B.  Oxidation 61 

C.  Reaction  of  the  Oxide  and  Water 61 

D.  Reaction  of  Potassium  and  Water 61 

E.  Action  of  Potassium  on  the  Dioxide  of  Carbon..  61 

F.  Reaction  of  Potassium  Hydroxide  and  Sul- 

phuric Acid 62 

31.  Nitrogen 63 

32.  A  Chemical  Investigation 63 

A.  Preparation  of  Nitric  Acid 64 

B.  Action  of  Magnesium  on  Nitric  AcidU ........  Q§ 


XVI  CONTENTS. 

Ex.  32.  A  Chemical  Investigation  PAGE 

C.  Action  of  Copper  on  Nitric  Acid 65 

Z>.  Action  of  Carbon  on  Nitric  Acid 66 

E.  Keaction  of  Nitric  Acid  and  Potassium  Hy- 
droxide   67 

33.  Ammonia 

A.  Preparation  of  Ammonia 68 

B.  Ammonia  Fountain 70 

C.  Salts  of  Ammonia 71 

34.  Oxides  of  Nitrogen 72 

PART  II.     ADDITIONAL  EXPERIMENTS. 

Ex.    1.  Bromine 77 

2.  Bromides 78 

A.  Properties  of  Hydrogen  Bromide 78 

B.  Sodium  Bromide 78 

(7.  Emplacement  of  Bromine 78 

3.  Iodine 

A.  Properties 79 

B.  Solubility 79 

C.  Action  on  the  Skin 79 

D.  Action  on  Starch 79 

4.  Iodides 

A.  Properties  of  Potassic  Iodide 80 

B.  Replacement  of  Iodine  by  Chlorine 80 

C.  Will  Bromine  Displace  Iodine  ?  81 

6.  Fluorine  and  Fluorides 

A.  Properties  of  Calcic  Fluoride 81 

B.  Preparation  of  Fluoride  of  Hydrogen 81 

C.  Etching  of  Glass  by  Hydrofluoric  Acid 82 

6.  Arsenic  and  its  Compounds 

A.  Properties  of  Arsenic 83 

B.  Oxidation 83 

C.  Reduction  of  the  Oxide  of  Arsenic 84 

D.  Arsenide  of  Hydrogen 84 

E.  Detection  of  Arsenic 85 

7.  Antimony 

A.  Properties ; 87 

B.  Oxidation 87 

C.  Chloride  ...  .88 


CONTENTS.  Xvii 

Ex.    7.  Antimony  PAGE 

D.  Hydrogen  Antimonide 88 

E.  A  Chemical  Examination 89 

8.  Bismuth 

A.  Properties 89 

B.  Nitrate  of  Bismuth 89 

9.  Tin 

A.  Properties 89 

B.  Oxidation 90 

C.  Crystalline  Structure 90 

D.  Action  of  Strong  Acids  with  Tin 90 

E.  Replacement  of  Tin  by  Zinc 91 

10.  Lead 

A.  Properties 91 

B.  Oxidation * 91 

C.  Action  of  Water  on  Oxide  of  Lead 91 

D.  Action  of  Acids  on  Lead 91 

E.  Replacement  of  Lead  by  Zinc 92 

F.  Lead  Chloride 92 

G.  Lead  Sulphate 92 

H.  Plumbers'  Solder 92 

7.  Fusible  Alloy 93 

11.  Silver 

A.  Properties 93 

B.  Oxidation 93 

C.  Action  of  Acids  on  Silver 93 

D.  Replacement  of  Silver  by  Copper 94 

E.  Replacement  of  Silver  by  Calcium,  Sodium 

and  Potassium 94 

F.  Sulphide  of  Silver 95 

G.  Oxide  of  Silver 95 

H.  Purification  of  Silver 95 

12.  Gold 

A.  Properties 96 

B.  Action  of  Acids  on  Gold 96 

C.  Chloride  of  Gold 97  " 

D.  Gold  Amalgam 97 

E.  Color  of  Gold 97 

13.  Platinum 

A.  Properties 98 


XV111  CONTENTS. 

Ex.  18.  Platinum  PAGE 

B.  Action  of  Acids  on  Platinum 98 

C.  Action  of  other  Chemicals,  besides  Acids,  on 

Platinum 98 

D.  Action  of  Metals  with  Platinum 98 

E.  Platinum  Sponge 98 

14.  Aluminum 

A.  Properties 99 

J5.  Oxidation 99 

(7.  Action  of  Acids  on  Aluminum 99 

D.  Sulphate  of  Aluminum 99 

E.  Alum .' 100 

PART  III.     HISTORY  AND  DEVELOPMENT  OF  THE  LAWS  AND  THEO- 
RIES or  CHEMISTRY. 

CHAPTER  I.     INTRODUCTION 103 

Physical  and  Chemical  Changes 103 

Ex.    1.  Two  kinds  of  Changes 104 

2.  Changes  caused  by  Water  of  Crystallization  106 

3.  Change  caused  by  the  Action  of  Sulphuric 

Acid  on  Water 106 

Analyses,  Syntheses,  and  Metatheses 107 

Ex.    4.  Synthesis  of  Chloride  of  Ammonium 108 

5.  Metatheses 110 

CHAPTER   II.     THE  EARLIEST  PERIOD Ill 

CHAPTER  III.     THE  PERIOD  OF  ALCHEMY 114 

Ex.    6.  A  So-called  Transmutation 116 

7.  Death  of  a  Metal 117 

8.  Resurrection  of  a  Metal 117 

CHAPTER  IV.     THE. MEDICAL  PERIOD... 120 

CHAPTER   V.     THE  PERIOD  OF  ROBERT  BOYLE 125 

Ex.    9.  The  Law  of  Boyle 126 

10.  Qualitative  Tests 132 

A.  Tests  used  by  Boyle 132 

B.  Tests  by  Physical  Changes 132 

C.  Tests  by  Chemical  Changes 133 

11.  Mechanical  Mixture  and  Chemical   Com- 

pound    135 

A.  Iron  and  Sulphur 135 

B.  Zinc  and  Sulphup .,,...  136 


CONTENTS.  XIX 

+• 

PAGE 

CHAPTER    VI.     THE  PHLOGISTON  PERIOD 138 

CHAPTER  VII.     THE  PNEUMATIC  PERIOD 140 

Ex.  12.  Weight  and  Specific  Gravity  of  Air 141 

13.  The  Law  of  Dalton 143 

14.  Weight  and  Specific  Gravity  of  Carbonic 

Dioxide  145 

15.  Weight  and  Specific  Gravity  of  Hydrogen 

Gas 148 

16.  Weight  and  Specific  Gravity  of  Illuminat- 

ing Gas 149 

17.  Conservation  of  Mass 157 

A.  The  Combustion  Products  of  a  Can- 

dle   157 

B.  The  Weight  of  the  Products  is  Equal 

to  the  Weight  of  the  Factors 159 

CHAPTER  VIII.  THE  MODERN,  OR  ATOMIC  THEORY,  PERIOD 161 

§  1.  Introductory 161 

Ex.  18.  Law  of  Definite  Proportions  by  Weight ....  163 
§2.  Quantitative  Analysis 164 

Ex.  19.  Analysis  of  Table  Salt 165 

§  3.  Multiple  Proportions 168 

Ex.  20.  Multiple  Proportions 169 

A.  The  Oxides  of  Sulphur 169 

B.  The  Oxides  of  Nitrogen 169 

C.  The  Chlorides  of  Iron 170 

§4.  Dalton's  Atomic  Theory 170 

§  5.  Combining  Number 172 

Ex.  21.  Determination  of  the  Combining  Number 

for  Zinc 172 

§  6.  Prout's  Hypothesis 175 

§7.  Molecules 176 

§  8.  Kelative  Weight  of  the  Atoms 177 

Ex.  22.  Law  of  Definite  Proportions  by  Volume....  179 
§  9.  The  Molecular  Theory 180 

Ex.23.  Spaces  between  the  Molecules 182 

24.  Irregular  Expansion  of  Liquids 184 

25.  Regular  Expansion  of  Gases 185 

§  10.  Determining  Atomic  Weights 192 


XX  CONTENTS. 

* 

PAGE 

§  11.  Determining  Molecular  Weights , 195 

Ex.  26.  Determination  of  Molecular  Weights  by 

the  Physical  Method 196 

A.  Molecular  Weight  of  Carbonic  Di- 

oxide     196 

B.  Molecular  Weight  of  Oxygen  Gas....  196 
27.  Determination  of  Molecular  Weights  by 

the  Chemical  Method 197 

A.  Molecular  Weight   of   Chlorate   of 

Potassium  198 

B.  Molecular  Weight  of   Chloride   of 

Potassium 199 

C.  Molecular  Weight  of   Sulphate  of 

Potassium 200 

§  12.  Specific  heat 202 

Heat 203 

Ex.  28.  Transference  of  Motion 203 

29.  Specific  Heat  of  Zinc 206 

30.  Specific  Heat  of  Iron 207 

31.  Specific  Heat 207 

Law  of  Dulong  and  Petit 208-209 

Determination  of  the  True  Atomic  Weight  of  Zinc 

from  its  Combining  Number  and  its  Specific  Heat..  210 

§  13.  Isomorphism 211 

Ex.  32.  Isomorphism 211 

§  14.  The  Periodic  Law 213 

Table  of  Atomic  Weights 216 

LANGUAGE  OP  CHEMISTRY 218 

Table  of  Atomic  Symbols 219 

STOICHIOMETRT 224 

MANIPULATIONS  226 

To  Mark  Glass 226 

To  Cut  Glass 226 

To  Fire-Polish  the  Edges  of  Glassware 228 

To  Bend  Glass  Tubes  and  Rods 228 

To  Draw  out  Glass  Tubes 229 

To  Make  a  Matrass 230 

To  Bender  Corks  Air-Tight 230 


CONTENTS.  XXI 


MANIPULATIONS 

To  Render  Joints  Air-Tight  ............................................................  231 

To  Cut  Rubber  Neatly  and  Quickly  ..........................................  ..  231 

To  Pass  a  Glass  Tube  through  a  Hole  in  a  Rubber  Stopper....  231 

To  Bore  a  Round  Hole  in  Glass  ....................................................  231 

To  Prevent  Mixing  Glass  Stoppers  ...............................................  232 

To  Hold  Hot  Beakers,  Test-Tubes,  etc  .....................  :  ..................  232 

To  Use  the  Pneumatic  Trough  ......................................................  232 

To  Use.  Filter  Papers  ........................................................................  233 

To  Dry  Bottles,  Flasks,  etc  .........................................................  234 

To  Remove  Stoppers  that  have  Stuck  ..........................................  234 

To  Pour  Gases  .................................................................................  235 

To  Use  a  Bunsen  Burner  ...............................................................  235 

To  Use  the  Bunsen  Blast-Lamp  ...............  ....................................  236 

APPENDICES  ...............................................................................................  237 

A.  Apparatus  for  the  Electrolytic  Decomposition  of  Water..  239 

B.  Hydrogen  Explosions  ...............................................................  241 

C.  Test  Papers  .............................................................................  242 

D.  Suction  Pumps  .........................................................................  243 

E.  Catch-Bottles  .............................................................................  244 

F.  Generator  for  Gases  ..................................................................  246 

G.  Hood  ...........................................................................................  247 

H.  Preparation  of  Chlorine  ..........................................................  247 

I.  Sodium  Amalgam  .....................................................................  248 

J.  Test  Solutions  ............................................................................  249 

K.  Use  of  the  Mouth  Blow-Pipe  ....................................................  250 

L.  Arsenical  and  Antimonial  Papers  for  Testing  ....................  250 

M.  To  Dry  Precipitates  .................................................................  251 

N.  To  Nurse  a  Crystal  ..................................................................  251 

0.  Distilled  Water  .........................................................................  252 

P.  Directions  for  a  Student  Who  Has  no  Instructor  ..............  254 

IXDEX  ...  259 


THE  student  should  provide  himself  with  a  blank- 
book  —  best,  one  with  no  ruling  whatever  —  with  pages 
not  less  than  six  by  eight  inches,  and  containing  not 
less  than  150  leaves;1  also  an  apron  large  enough  to 
cover  chest  as  well  as  legs,  or,  better,  overalls  and  a 
light,  cheap  workingman's  jacket.  Before  the  time 
appointed  for  the  first  work  in  the  laboratory  he  should 
apply  to  his  instructor  for  the  assignment  of  desk, 
apparatus,  and  chemicals,  and  the  directions  for  begin- 
ning work.2 

The  first  three  exercises  are  preliminary  to  the  regu- 
lar work.  Their  chief  purpose  is  to  enable  the  pupil  to 
form  the  acquaintance  of  the  system  of  weights  and 
measures  used  in  scientific  work,  and  to  accustom  him- 
self to  the  use  of  apparatus. 

In  all  scientific  work  it  must  be  the  student's  aim  to 
observe,  to  experiment,  to  reason.  His  goal  is  the  Truth. 
Let  him  continually  ask  the  question  "  Why?  "  The 

1  Experience  has  shown  that  it  is  best  to  get  a  blank-book  with 
leather  back  and  tips.     Such  a  book  should  not  cost  over  thirty-five 
or  forty  cents.     Laboratory  usage  is  apt  to  destroy  the  light  cloth 
back  of  the  ordinary  pasteboard-covered  blank-book.     The  common 
blank-book  also  quickly  wears  out  at  the  corners,  and,  as  the  leather 
tips  cost  but  little,  they  are  recommended. 

2  A  student  who  is  going  to  use  this  book  without  an  instructor  will 
find  his  directions  in  Appendix  P.    ,  ->-"" "' 

- 


XXIV  LNTKODUCTION. 

laboratory  note-book  must  be  a  store-house  for  the 
observations  from  the  experiments.  A  full  page  should 
be  reserved  before  beginning  the  description  of  any 
experiment  [or  before  that  of  every  part  of  an  experi- 
ment when  the  parts  themselves  are  long  or  promise  to 
demand  much  arithmetical  calculation].  On  this  page 
the  student  should  put  his  first  rough  notes  at  the  moment 
the  observations  are  made.  Here  also  should  appear  all 
figuring,  the  results  of  which  only  he  wishes  to  appear 
in  the  course  of  his  description.  There  must  be  no 
note-taking  nor  figuring  of  any  kind  on  bits  of  paper, 
apparatus,  etc.  All  the  notes,  and  the  whole  figuring 
for  mathematical  problems  must  appear.  Remember 
that  a  page  is  particularly  reserved  for  this  rough  work, 
and  the  student  must  not  allow  himself  to  form  the 
habit  of  entrusting  his  notes  to  papers,  that  are  always 
apt  to  be  misplaced  or  destroyed.  Moreover,  if  a  mis- 
take has  been  made  in  number  only,  it  is  irritating, 
indeed,  to  be  obliged  to  repeat  all  the  experiment 
when,  if  the  original  data  were  present,  the  mistake 
could  be  corrected,  often  at  a  glance.  Do  not  correct 
mistakes  by  erasure  and  rewriting.  Cross  out  the  old 
and  let  the  new  appear  by  its  side.  Do  not  fear 
that  this  method  will  spoil  the  appearance  of  the  book 
in  the  eyes  of  the  instructor.  Every  instructor  of 
experience  knows  that,  though  greatly  to  be  sought 
after,  infallibility  is  not  attainable  by  a  beginner  in 
laboratory  work,  or,  in  fact,  by  any  other  student, 
while  erasures,  even  by  the  best  of  students,  must  be 
looked  at  with  some  suspicion.  Try,  however,  to  con- 
fine all  correction  of  mistakes  to  these  pages  just 


INTRODUCTION.  XXV 

mentioned  as  reserved  for  rough  notes  and  figuring.  Do 
not  attempt  to  write  the  fair  account  of  the  experiment 
till  the  experiment  has  been  performed  completely  and 
satisfactorily  in  the  laboratory  and  the  necessary  ob- 
servations and  calculations  [if  any]  have  been  made  on 
the  preliminary  page.  When  the  experiment  is  thus 
finished,  and  every  question  that  has  arisen  in  con- 
nection with  it  has  been  answered,  and  the  whole  is 
fully  understood,  then  write  out  on  the  page  [or  pages] 
following  the  preliminary  page,  a  good,  clear  statement 
of  the  experiment,  making  evident  to  any  future  reader 
the  apparatus  and  material  used  ;  the  method  followed  ; 
what  has  been  observed  ;  and  the  conclusion  drawn,  or 
what  the  experiment  has  shown.  Ink  should  be  used 
for  writing  this  account  if  it  is  desired  that  the  note- 
book shall  have  the  neatest  possible  appearance  at  the 
end  of  the  year.  The  preliminary  page,  however,  best 
be  kept  in  pencil.  It  has  been  found  a  good  plan  to 
reserve  all  left-hand  pages  for  preliminary  pages,  and 
all  right-hand  pages  for  the  account  written  in  ink. 

Although  some  pupils  seem  to  profit  by  thinking 
over  an  experiment  for  a  day  or  two,  after  having  made 
their  preliminary  rough  notes,  before  writing  the  per- 
manent account,  yet  there  is  danger  of  forming  in  this 
way  a  habit  of  negligence.  In  general,  the  full  account 
should  be  completed  not  later  than  one  week  from  the 
time  the  experiment  was  done  in  the  laboratory. 

Represent  apparatus,  crystalline  forms,  etc.,  as  far  as 
possible,  by  sketches.  A  drawing  will  often  express 
clearly  and  forcibly  as  much  as  pages  of  writing.  Do 
not  feel  discouraged  if  the  first  drawings  seem  failures. 


XXVI  INTKODUCTION. 

Make  good  use  of  the  eyes  and  resolve  that  each  suc- 
ceeding figure  shall  be  a  little  better  than  the  one 
before,  and  there  need  be  no  fear  for  the  appearance  of 
the  last. 

Be  sure  to  insert  an  answer  in  the  laboratory-book 
every  time  a  question  is  asked  in  the  text-book.  Make 
this  answer  in  the  form  of  a  statement  in  such  a  way 
that  the  answer  may  be  understood  by  a  person  who 
does  not  know  the  question.  First  formulate  an 
answer  to  every  question,  and  then  turn  to  the  in- 
structor and  ascertain  if  the  answer  is  correct,  before 
writing  it  in  the  note-book.  It  seems  to  the  author 
that  every  teacher  should  pay  particular  attention  to 
this  or  some  similar  method  of  questioning,  as  it 
teaches  the  student  to  do  his  own  thinking,  and  gives 
the  instructor  a  chance  to  watch  the  working  of  the 
student's  mind  with  a  view  to  giving  help  to  the 
student  in  acquiring  correct  methods  of  reasoning. 

Particular  attention  should  also  be  given  to  express- 
ing chemical  changes  by  means  of  diagrams,  as  on  page 
32,  but  it  is  not  advisable  to  use  chemical  symbols  for 
abbreviations  in  these  diagrams,  even  if  the  student 
thinks  he  knows  the  full  significance  of  a  chemical 
symbol. 

At  Exeter  the  instructor  meets  the  students,  in  class, 
four  times  a  week.  In  general,  at  each  of  the  first 
three  of  the  four  periods  he  assigns  some  new  work 
to  be  done  in  the  laboratory,  gives  any  needed  direc- 
tions or  precautions,  and  then  holds  a  review  of  the 
work  that  was  assigned  one  week  before.  In  these 
reviews  the  experiments  are  taken  up  in  their  order, 


INTRODUCTION.  XXvii 

the  questions  in  the  text  are  put  to  the  students,  and 
the  instructor  endeavors  to  find  out,  and  clear  away, 
any  difficulties  his  students  may  have  met.  At  the 
fourth  period,  which  is  the  last  in  the  week,  the 
instructor  has  his  students  write  out  the  fair  accounts 
in  ink.  While  they  are  writing  he  passes  among  them, 
examines  their  books,  and  criticises,  —  particularly, 
their  manner  of  recording  the  work  done.  This 
fourth  period  has  come  to  be,  at  Exeter,  a  period 
of  instruction  in  English  composition  as  well  as  in 
chemistry.  Between  these  four  periods  the  students, 
still  under  the  direct  oversight  of  the  instructor,  per- 
form their  experiments  in  the  laboratory,  and  make 
their  rough  preliminary  notes.  About  100  hours  of 
laboratory  work  have  been  found  necessary,  by  the 
most  careful  workers,  to  complete  Part  I.  Part  II  re- 
quires about  fifty  hours,  and  the  experimental  work  of 
Part  III  requires  about  fifty  hours.1  If  a  student  has 
only  a  limited  amount  of  time  to  devote  to  his  chem- 
istry, the  author  advises  him  to  take  Part  III  after 
finishing  Part  I. 

1  It  is  hoped  that  students  who  take  up  this  course  in  chemistry 
will  have  had  such  laboratory  practice  in  physics  that  they  can  omit 
the  actual  performance  of  many  experiments  of  Part  III,  e.g.,  "Law 
of  Boyle";  "Weight  and  Sp.  Gv.  of  Air";  "  Law  of  Dalton  ";  Ex- 
periments 14,  15  and  16  on  the  Sp.  Gv.  of  gases  ;  "  Spaces  between 
the  Molecules";  "Irregular  Expansion  of  Liquids";  "Regular 
Expansion  of  Gases";  and  the  experiments  under  Sp.  Heat.  In 
every  case  of  omission,  however,  reference  should  be  made  to  the 
data  already  prepared  and  recorded  in  the  note-book  of  physics,  and 
the  results  should  be  carefully  reviewed  for  use  in  the  work  in 
chemistry. 

The  fifty  hours  noted  above  are  for  a  student  who  has  not  had 
previous  training  in  Physics. 


XXV111  INTRODUCTION. 

Part  II  contains  work  of  the  same  nature  as  that  of 
Part  I.  This  additional  work,  on  highly  interesting 
substances,  is  intended  for  students  who  can  devote 
more  time  to  their  chemistry  than  those  who  are  limited 
to  the  minimum  that  is  necessary  for  a  general  edu- 
cation. It  is  possible  to  arrange  the  work  so  that  the 
brightest  students  in  a  class  may  do  both  Part  I  and  Part 
II  while  those  of  average  ability  are  doing  Part  I,  e.g., 
bright  students  may  be  allowed  to  work  ahead  of  the 
class,  putting  only  their  rough  notes  in  the  note-book 
till  the  class,  in  review,  has  caught  up  ;  or  two  sections 
of  the  class  may  be  formed.  But  no  experiment  of 
Part  I  should  be  omitted  by  any  one. 

When  the  student  is  in  the  laboratory  he  should  be 
careful  always  :  — 

To  read  through  the  description  of  each  part  of 
every  experiment  before  commencing  to  do  that 
part. 

To  note  carefully  all  cautions. 

To  leave  balances  clean  and  in  proper  adjustment. 

To  keep  all  weights  clean. 

To  resist  the  temptation  to  use  weights  for  any 
other  purpose  than  weighing. 

To  avoid  putting  test  papers  in  liquids.  [See 
Appendix  C.] 

To  use  only  clean  apparatus. 

To  put  on  the  preliminary  page  of  the  note-book 
only  brief  notes,  and  notes  right  to  the  point. 

To  use  the  utmost  care  in  all  work  with  hydrogen 


INTRODUCTION.  XXIX 

And  at  all  times  :  — 

To  use  his  utmost  good  judgment,  and  if  in 
difficulty  or  in  danger,  to  try  to  think  his  way  out 
clearly  and  quickly. 

Chemicals  and  apparatus  should  be  provided  well  in 
advance  of  the  time  they  will  be  needed,  in  order  that 
there  may  be  no  loss  of  time  in  waiting  for  suitable 
apparatus  or  the  necessary  chemicals. 

Mr.  M.  A.  Buck,  at  5  Tremont  Street,  Boston,  is 
prepared  to  furnish  apparatus  and  chemicals  suited  to 
the  needs  of  students  who  pursue  this  course.  On 
application,  he  will  furnish  carefully  prepared  lists 
of  all  apparatus  and  chemicals  needed,  either  for  the 
whole  book  or  for  any  part,  —  for  a  liberal  allowance, 
or  for  the  minimum  amount  required  by  careful  stu- 
dents,—  and  his  arrangements  are  such  that  he  can 
usually  furnish  the  articles,  whether  ordered  in  com- 
plete sets  or  individually,  at  prices  below  the  dealers' 
regular  quotations. 

As  Mr.  Buck  was  an  assistant  in  the  Exeter  Labora- 
tory for  several  years  during  the  development  of  this 
course,  the  author  feels  sure  that  he  will  prove  well 
fitted  to  furnish  exactly  the  right  articles  to  make  the 
work  run  with  the  least  amount  of  friction  from 
"misfit"  apparatus  and  chemicals  unsuited  for  the 
work  in  hand. 


PRELIMINARY  WORK, 


PRELlMr^rART  WORK. 

IN   THE   LABORATORY. 
I.     MEASURING. 

HAVE  ready  a  metric  rule,  about  thirty  centimeters 
long  and  graduated  to  millimeters ;  a  rule  about  one 
foot  long  and  graduated  in  inches  and  fractions  of 
inches,  down  at  least  to  one  eighth  inch;1  a  glass 
cylinder,  capacity  50  or  100  cubic  centimeters,  and 
graduated  to  cubic  centimeters;  a  graduate  holding 
one  fluid  ounce ;  several  glass  beakers,  flasks,  and 
bottles  of  different  sizes;  a  test-tube  rack  containing 
five  or  six  test-tubes  of  different  sizes. 

Measure,  first  in  the  metric  system,  then  in  the 
English,  the  length  of  your  laboratory  desk;  also  its 
width;  estimate  its  area  in  square  centimeters,  in 
square  inches,  in  square  millimeters,  in  square  meters. 
In  recording  measurements  use  the  decimal  point,  e.g., 
if  the  length  of  your  desk  is  one  meter,  and  two  deci- 
meters, and  five  centimeters,  and  seven  millimeters,  do 
not  record  the  measurement  lm,  2dm,  5cm,  and  7mm;  but 
express  it  1.257m,  or  125.7cm,  or  the  like.  How  many 
centimeters  are  there  in  one  inch  ?  How  many  inches 
in  one  meter?  How  many  square  centimeters  in  one 

1  A  convenient  form  of  rule  is  one  having  centimeters  on  one  side 
and  inches  on  the  other. 


4  PRELIMINARY   WORK. 

square  inch?  What  fraction  of  a  square  inch  does 
a  square  centimeter  occupy  ?  Put  the  answers  to  these 
questions  in  your  note-book.  Also  fix  the  round  num- 
bers in  your  mind. 

Take  your  graduated  cylinder  [commonly  called 
44  graduate  "],  fill  your  largest  flask  to  the  brim  with 
water,  pour  the  water  from  the  flask  into  the  cylinder, 
and  find  how  many  cubic  centimeters  the  flask  holds. 
Find  also  the  capacity  in  cc  [cc  stands  for  cubic  centi- 
meters] of  your  other  flasks,  beakers,  bottles,  and  test- 
tubes. 

One  purpose  of  this  work  in  measuring  is  to  enable 
you  to  tell  at  a  glance  about  how  much  the  laboratory 
vessels  in  common  use  contain.  It  is  best,  then,  in 
making  these  measurements,  not  to  fill  the  beakers  to 
the  brim,  but  conveniently  full  only.  Try  to  fix  the 
various  capacities  in  mind. 

Also  find  the  capacity  of  at  least  two  bottles,  your 
smallest  beaker,  and  a  test-tube  in  fluid  ounces,  using 
your  oz.  graduate  as  a  measure.  Fix  the  values  in  mind 
as  well  as  record  them  in  your  note-book.  Bottles  are 
commonly  designated,  in  trade,  by  the  number  of  ozs. 
they  contain. 

II.     WEIGHING. 

Have  ready  a  platform  balance,  capable  of  holding  a 
load  of  5  kilos  and  sensitive  at  least  to  one  tenth  of 
a  gram;  a  set  of  iron  weights,  2000-10g  inclusive 
[g  stands  for  gram,  sometimes  written  gramme];  a 
smaller  balance,  sensitive  at  least  to  one  one  hundredth 
of  a  gram;  a  set  of  weights,  50g-10mg  inclusive  [mg 


PRELIMINARY   WORK.  5 

stands  for  milligrams],  accurate  at  least  to  one  one 
hundredth  of  a  gram ;  a  pair  of  brass  forceps  for  hand- 
ling the  weights. 

Take  the  large  balances,  fill  three  of  your  larger 
vessels  conveniently  full  of  water;  weigh  each  sepa- 
rately, then  all  three  together.  Weigh  accurately  to  a 
single  gram.  See  if  the  sum  of  the  three  separate 
weights  equals  the  combined  weight.  Record  all  ob- 
servations in  your  note-book.  In  recording  use  the 
decimal  point  as  in  the  case  of  your  measurements. 

Balance  your  graduate  on  one  pan  with  any  con- 
venient article,  as,  for  instance,  a  vessel  partly  filled 
with  water  or,  better,  with  lead  shot.1  Pour  water  into 
the  graduate  to  the  amount  of  exactly  50CC  [100CC  if 
you  have  a  100CC  graduate].  Get  the  weight  of  this 
water  and  notice  that  one  cc  of  water  weighs  exactly 
one  gram. 

Take  the  smaller  balances,  and,  using  the  smaller 
weights  [which  must  be  handled  with  the  forceps  only], 
weigh  [accurately  to  centigrams2]  three  nails,  first  sep- 
arately, then  all  together.  The  sum  of  the  separate 
weights  should  not  vary  from  the  combined  weight 
more  than  0.05g.  If  the  variation  is  greater,  repeat  all 
the  weighings.  Record  results  showing  the  variation, 
if  any.3 

1  It  is  a  good  plan  always  to  have  at  hand  in  the  laboratory  two  or 
three  saucers  or  similar  stout  vessels  filled  with  shot,  to  be  used  for 
balancing  vessels  whose  contents  only  are  to  be  weighed  accurately. 

2  If  you  are  not  familiar  with  the  denominations  of  the  metric 
system,  look  up  this  system  in  some  arithmetic  or  in  the  dictionary. 

3  Unless  perfectly  familiar  with  the  English  system  of  weights  and 
the  relation  between  these  weights  and  the  metric,  obtain  a  set  of 
English  weights,  and  with  these  weigh  all  the  articles  you  have 


PRELIMINARY   WORK. 


III.     MAKING  A    WASH-BOTTLE. 

Take  a  500CC  flask  and  a  cork  to  fit ;  also  about  1 
meter  of  soft  glass  tube  with  a  bore  of  about  6mra 
[mm  stands  for  millimeters].  Put  the  cork  on  the  floor 
and  with  the  sole  of  the  shoe  roll  it  to  soften  it  and 
make  it  fit  the  neck  of  the  flask  tightly.  With  a  rat- 
tail  file  bore  two  holes  through  the  cork.  Let  each 
hole  be  round  and  of  such  size  that  the  glass  tube  will 
fit  it  tightly.  Take  a  piece  of  the  glass  tube  about 
10cm  [cm  stands  for  centimeters]  longer  than  the  height 
of  the  flask.1  Stand  the  glass  tube  in  the  flask,  make 
a  mark  on  the  tube  half  way  between  its  upper  end 
and  the  top  of  the  flask.2  Bend  the  glass  tube8  at  the 
mark  until  the  shorter  limb  forms  with  the  longer  an 
angle  of  about  45°.  The  bend  should  form  a  curve, 
not  a  sharp  angle.  Pass  the  longer  limb  through  a 
hole  of  the  stopper,  then  at  a  point  about  half  way 
between  the  first  bend  and  the  open  end  of  the  longer 
limb,  make  another  but  lesser  bend.  This  latter  bend 
should  bring  the  lower  end  of  the  tube,  when  the  cork 
is  inserted  in  the  flask,  to  the  vertex  of  the  angle  made 
by  the  bottom  of  the  flask  with  its  side.  Be  sure  to 
make  the  second  bend  toward  the  first,  i.e.,  in  making 
the  second  let  the  open  end  of  the  longer  limb  approach 
the  open  end  of  the  shorter  limb  —  not  recede  still 

weighed  with  your  metric  weights.  Compare  results,  and  note  that 
one  ounce  is  equal  to  about  28.3  grams  and  that  one  pound  contains 
about  454  grams. 

1  To  cut  glass  tubes,  see  Manipulations  [at  end  of  book]. 

2  To  mark  tubes,  see  Manipulations. 
8  See  Manipulations. 


PRELIMINARY    WORK.  7 

farther  from  it.  Now  take  a  piece  of  glass  tube  about 
15  centimeters  long,  bend  this  slightly,  best  till  the 
two  limbs  form  an  obtuse  angle  of  135°.  Take  a  third 
piece  of  glass  tube  and  draw  it  out1  to  a  diameter  of 
about  2mm.  From  this  drawn-out  tube  cut  a  tip  for  the 
wash-bottle.  At  one  end  this  tip  should  be  of  the  same 
diameter  as  the  original  tube;  at  the  other,  not  over 
2mm ;  in  length,  3-5cin.  Wipe  all  soot  from  the  three 
tubes.  Fire  polish2  every  rough  end  of  the  tubes. 
Insert  the  second  bent  tube  through  its  hole  in  the 
cork,  letting  the  end  be  flush  with  the  lower  end  of 
the  cork.  This  tube  forms  the  mouth-piece.  Attach, 
by  means  of  a  rubber  connector,  i.e.,  a  piece  of  small 
rubber  tube  l-2cm  long,  the  tip  to  the  shorter  end  of 
the  longer  bent  tube.  This  tip  forms  the  jet,  and, 
owing  to  its  flexible  connection  of  rubber,  can  be 
directed  by  the  fingers  in  different  directions  when  the 
wash-bottle  is  used  for  washing  precipitates.  The 
slight  inner  bend  in  the  longer  tube  enables  the  whole 
of  the  water  to  be  blown  from  the  bottle  when  the  flask 
is  tipped  up,  as  it  usually  is,  in  use.  Fill  the  bottle 
about  two  thirds  with  water.  [Distilled  water3  is  best, 
though  not  necessary,  for  the  following  experiments. 
When  necessary,  the  fact  will  be  stated.]  Wet  the 
cork  to  fill  the  pores,  insert  the  cork  in  the  flask,  and 
blow  through  the  mouth-piece.  The  tip  should  deliver 
a  fine,  steady  stream.  Insert  a  sketch  of  your  wash- 
bottle  in  your  note-book. 

1  See  Manipulations.        2  See  Manipulations.        3  See  Appendix  O. 


PART   I. 


EXPERIMENTS 


PART  I.  — EXPERIMENTS. 


Experiment  1. 
Iron.  —  A  solid  substance. 
A.     The  Properties  of  Iron. 

TAKE  an  iron  nail  and  a  piece  of  fine  iron  wire. 
Note  as  many  of  the  properties  of  iron  as  you  can,  e.g., 
color  [make  a  fresh  scratch  with  a  file  to  get  the  true 
color] ;  hardness  [see  what  it  will  scratch,  and  what 
will  scratch  it,  —  try,  for  instance,  glass,  chalk,  wood,  a 
file,  etc.] ;  tenacity  [try  pulling  apart  the  nail,  the 
wire] ;  brittleness  [mention  some  things  you  find,  on 
trying,  to  be  more  brittle,  some  less] ;  fusibility  [try  to 
melt  the  wire,  first  in  the  flame  of  the  Bunsen  burner,1 
then  in  that  of  the  blast-lamp] ;  volatility  [see  if  any 
heat  you  can  produce  will  make  it  go  off  in  vapor  in 
the  way  steam  does  from  hot  water]. 

B.     Action  of  Air  on  Hot  Iron. 

Fill  a  small  porcelain  crucible  about  half  full  of  iron 
filings.  Weigh  carefully  [to  centigrams].  Set  the 
crucible  on  a  pipe-stem  triangle  supported  on  a  stand. 
Heat  with  a  Bunsen  burner  for  about  ten  minutes  with 
occasional  stirring  [with  a  glass  rod],  that  the  air  may" 
come  in  contact  with  all  the  filings.  Cool  the  crucible. 

1  For  the  use  of  burners,  see  Manipulations. 


12  IRON. 

Why?  Again  weigh.  What  has  caused  the  gain? 
See  if  you  can  detect  any  difference  of  lustre  between 
filings  not  heated  in  air  and  those  heated.  Sprinkle 
a  few  filings  in  the  flame  and  note  the  phenomenon. 
What  is  a  phenomenon?  Do  not  return  filings  once 
used  to  the  bottle.  Let  us  call  that  which  has  come 
from  the  air  and  fastened  itself  to  the  filings — oxygen, 
and  the  new  dull-black  substance  formed  —  oxide  of 
iron.  Let  us  call  oxide  of  iron  a  compound,  because 
it  is  obviously  compounded  of  two  other  substances. 
Let  us  call  iron  itself  a  simple  substance,  because 
we  cannot  make  it  from  two  or  more  other  substances, 
nor  can  we  get  two  or  more  other  substances  from  it. 
What  is  a  simple  substance  ?  What  is  a  compound  ? 

Having  found  that  there  is  in  the  air  a  peculiar  sub- 
stance capable  of  joining  iron,  it  becomes  of  interest  to 
ascertain  what  proportion  of  the  air  this  substance 
occupies.  In  our  investigation  we  shall  need  the  aid 
of  another  simple  substance,  phosphorus,  with  which 
the  oxygen  unites  even  more  readily  than  with  iron. 


Experiment  2. 

Phosphorus.— Another  solid  substance. 
A.     The  Properties  of  Phosphorus. 

Take  a  piece  of  yellow  phosphorus  and  a  little  red 
phosphorus. 

Caution  !  Caution  !  Caution  ! 

Yellow   phosphorus    is    very   poisonous    indeed,    ex- 
tremely inflammable,  and  a  phosphorous  burn  is  very 


PHOSPHORUS.  13 

painful.  This  substance  must  be  stored  under  water, 
and  cut  only  under  water,  —  best  in  the  pneumatic 
trough  or  in  a  large  basin.  Matches  must  not  be  kept 
in  closets  or  drawers. 

Examine  the  phosphorus  and  note  its  most  important 
properties,  as  color,  consistency,  fusibility,  inflamma- 
bility, etc.  Do  not  handle  the  yellow  with  bare  fingers. 
Use  iron  forceps.  Dry  it  rapidly  by  pressing  it  gently 
between  filter  or  blotting  papers.  In  stating  the  prop- 
erties, make  two  tables :  one  for  the  red,  the  other  for 
the  yellow. 

B.     Action  of  Air  on  Warm  Phosphorus. 

Have  ready  a  dry,1  quick-sealing  pint  fruit-jar,2  and  a 
clean  iron  deflagrating  spoon,  also  about  half  a  gram 
of  phosphorus.  If  you  use  the  yellow  phosphorus  it 
must  be  cut  under  water,  dried  quickly  by  pressing 
between  filter  papers,  and  at  once  placed  in  the  spoon. 
Have  at  hand  a  Bunsen  burner  flame,  over  which  the 
spoon  may  be  held  in  order  to  light  the  phosphorus. 

The  rubber  washer  to  the  jar  should  be  greased 
[vaseline  is  good]  to  make  it  tight.  Hold  the  spoon 
in  one  hand  and  the  cover  to  the  jar  in  the  other. 
Light  the  phosphorus,  and  with  a  quick  but  deliberate 
motion  plunge  the  spoon  in  the  jar,  at  once  put  on  the 
cover,  fasten  it  and  step  back,  as  the  jar  may  crack. 

Note,  as  the  phosphorus  burns  away,  the  white 
powder  formed.  As  soon  as  the  jar  cools,  open  it, 

• 

1  To  dry  flasks,  jars,  and  other  pieces  of  apparatus,  see  Manipula- 
tions. 

2  A  quick-sealing  fruit-jar  with  a  rubber  washer.     Those  called 
"Lightning"  are  excellent. 


14  MERCURY   AND   CARBON. 

holding  the  mouth  under  water,  which,  rushing  in,  will 
show  that  a  part  of  the  air  has  gone.  Make  a  rough 
estimation  of  what  part  [by  volume]  has  gone.  This  is 
the  same  part  that,  in  Ex.  1,  B,  left  the  air,  joined  the 
iron,  and  increased  the  weight.  Remember  that  we  are 
going  to  call  this  gas  which  has  the  power  of  joining 
other  things,  oxygen.  We  will  call  the  new  substance 
made  from  the  oxygen  and  the  phosphorus  [the  white 
powder  that  formed  in  the  jar]  oxide  of  phosphorus. 
Note  that  not  all  the  air  was  used, — part  was  left. 
This  part  is  another  gaseous  substance  which  we  shall 
study  later. 


Experiment  3. 
Mercury.  — A  liquid  substance. 

Caution!  Be  careful  in  the  use  of  heat  with  mer- 
cury, as  the  vapor  of  mercury  is  a  vigorous  poison. 
Take  a  globule  of  mercury  as  large  as  a  pea  and  note 
its  chief  properties.  In  doing  this,  review  Ex.  1,  A, 
and  Ex.  2,  A.  Note  those  respects  in  which  mercury 
resembles  iron  or  phosphorus,  and  those  in  which  it 
differs  from  these  substances. 


Experiment  4. 
Carbpn. 

Take  a  bit  of  charcoal,  a  bit  of  graphite  [from  a 
44 lead"  pencil],  some  soot,  a  bit  of  gas-retort  carbon, 
and  [if  obtainable]  a  diamond.  Also  burn  a  piece  of 


UBITBESITTI 


OXYGEN. 


thin  paper  to  get  the  carbonaceous  residue,  which  often 
keeps  the  original  form.  Study  these  different  forms 
of  carbon  and  note  chief  properties.  What  is  meant  by 
allotropic  forms  ? 


Experiment  5. 
Artificial  Preparation  of  Oxygen. 

A.     From  the  Red  Oxide  of  Mercury. 

Take  a  piece  of  hard  glass  tube,  and  red  oxide  of 
mercury.  Caution !  Red  oxide  of  mercury  is  a  vigorous 
poison.  Note.  Red  oxide  of  mercury  may  be  made  by 
prolonged  heating  of  mercury  in  contact  with  air.  Re- 
call the  preparation  of  the  black  oxide  of  iron  that  you 
made  in  Ex.  1,  B.  If  the  red  oxide  of  mercury  itself 
is  heated  vigorously,  it  is  separated  into  the  mercury 
and  the  oxygen  from  which  it  was  made. 

Make  a  small  matrass1  from  hard  glass  tube.  Fill 
the  bulb  about  one  half  with  the  red  oxide  of  mercury, 
and  heat  over  the  Bunsen  burner  flame.  Test  for 
oxygen  by  plunging  down  the  tube  a  bit  of  glowing 
[not  flaming]  carbon  [best  made  from  a  splinter  of 
wood  or  a  burned  match].  What  did  we  call  the  sub- 
stance formed  in  Ex.  1,  B,  when  oxygen  joined  the  iron 
filings?  what  the  substance  formed  from  the  union  of 
oxygen  and  phosphorus  when,  in  Ex.  2,  B,  the  phos- 
phorus burned?  What,  then,  shall  we  call  the  sub- 
stance formed  when  the  oxygen  now  joins  the  carbon, 
causing  the  intense  heat  and  fire  at  the  end  of  the 
splinter?  What  becomes  of  this  new  substance  which 
1  See  Matrass,  under  Manipulations. 


16  OXYGEN. 

is  formed?  Note  the  globules  that  collect  in  the  cool 
part  of  the  tube.  Break  open  the  tube  and  examine 
them.  What  are  they  ? 

This  process,  by  which  a  compound  substance  is  split 
into  simpler  ones,  is  called  Analysis,  and  is  typical  of  a 
vast  number  of  chemical  changes. 

B.     From  Chlorate  of  Potassium. 

Note.  As  red  oxide  of  mercury  is  expensive,  come 
other  method  than  that  of  part  A  is  desirable  for  pre- 
paring oxygen  on  the  large  scale.  It  is  found  that 
chlorate  of  potassium,  when  heated  to  a  high  tempera- 
ture, is  also  broken  up  into  two  substances,  one  of 
which  is  oxygen. 

Have  ready  a  Kjeldahl  flask1  clamped  to  a  stand  at 
such  a  height  that  the  body  of  the  flask  may  be  heated 
conveniently  by  a  Bunsen  burner.  Fit  the  flask  with  a 
one-hole  cork,  and  from  the  cork  let  a  glass  tube,  of  not 
less  than  5mm  bore,  pass  down  into  a  trough  of  water.2 
The  end  of  the  delivery  tube3  should  be  turned  up  a 
little  in  the  water.  Soak  the  cork  for  a  minute  or  two 
to  fill  small  holes. 

Put  in  the  flask  about  15g  of  chlorate  of  potassium. 
Weigh  the  flask  with  its  charge.  Do  not  have  the 
cork  in  when  you  weigh.  Clamp  the  flask  in  position. 
Caution !  In  this  experiment  never  insert  the  cork 
tightly,  as  the  tube  may  plug  up,  and  if  the  cork  cannot 

1  A  stout,  long-necked,  pear-shaped  flask  of  hard  glass. 

2  See  Pneumatic  Trough,  under  Manipulations. 

8  The  term  "delivery  tube"  will  appear  frequently  hereafter,  and 
is  to  be  taken  to  mean  a  tube  for  the  delivery  of  a  gas  from  a  flask, 
bottle,  or  the  like. 


OXYGEN.  17 

blow  out  [like  a  safety  valve],  the  flask  may  explode. 
Have  ready  four  pint  jars  filled  with  water  and  stand- 
ing inverted  on  the  bridge  of  the  pneumatic  trough. 
What  does  pneumatic  mean?  Heat  the  chlorate  of 
potassium  with  a  Bunsen  burner.  Caution!  Do  not 
allow  the  hand  .to  come  directly  under  the  flask,  for 
if  the  flask  should  crack  and  the  hot,  melted  chlorate 
run  out,  the  hand  might  be  scalded.  Move  the  flame 
all  around  on  the  bottom  of  the  flask  in  order  that  no 
part  of  the  glass  may  get  too  hot  and  soften.  Catch 
the  gas  evolved.  Catch  at  least  four  jars  full.  Not 
more  than  a  few  cc  of  water  should  be  left  in  a  jar. 
Snap  on  the  covers  while  the  jars  are  still  inverted  with 
their  mouths  under  water.  Use  rubber  washers,  well 
greased,  when  sealing  the  jars.  Set  the  jars  of  gas 
away  for  further  use.  Uncork  your  flask  before  you 
stop  heating  it.  Why?  Weigh  the  flask  with  the 
residue.  Compare  weight  with  first  weight.  Explain 
the  change  in  weight.  Take  your  first-caught  jar  of 
gas,  and  prove  that  the  gas  is  similar  to  that  from  the 
red  oxide  of  mercury,  ^.e.,that  it  is  oxygen.  Prove  this 
by  plunging  in  a  bit  of  glowing  carbon. 


Experiment  6. 
A.    Action  of  Undiluted  Oxygen  Gas  on  Iron. 

Have  ready  a  jar  of  oxygen  gas  [from  Ex.  5,  B],  also 
a  small  amount  of  very  fine  iron  filings.  Two  minutes' 
continuous  filing  of  a  board  nail  with  a  five  or  six-inch 
file  over  glazed  paper  furnishes  an  ample  amount  of 


18  OXYGEN. 

good  filings.  Those  used  in  trade  often  are  not  fit  for 
this  experiment.  Place  the  filings  in  a  little  heap  in  a 
clean  and  dry  deflagrating  spoon.1  Heat  them  [spoon 
and  all]  over  a  Buiisen  burner  for  a  moment  till  a  dull 
glow  runs  through  the  heap  ;  then  plunge  them  at  once 
into  the  jar  of  oxygen  and  put  on  the  cover.  Compare 
the  action  of  pure  oxygen  gas  with  that  of  the  oxygen 
in  the  air  [see  Ex.  1,  B],  which  is  diluted  with  nearly 
eighty  per  cent  [by  volume]  of  another  gas.  Save  the 
oxide  of  iron  for  Ex.  15. 

B.     Action  of  Undiluted  Oxygen  Gas  on  Phosphorus. 

Proceed  as  in  Ex.  2,  B,  except  that  the  phosphorus 
is  to  be  burned  in  a  jar  of  pure  oxygen  and  greater 
precautions  in  every  way  are  to  be  taken,  as  the  action 
is  violent  and  the  danger  of  the  jar  exploding  much 
greater.  Weigh  the  phosphorus  exactly.  In  no  case 
use  more  than  .55g  for  a  pint  jar.  It  is  best  to  throw  a 
cloth  around  the  jar  after  the  action  and  keep  the  cloth 
around  till  the  jar  is  opened  under  water.  This  will 
catch  pieces  of  glass  if  there  is  an  explosion.  What 
becomes  of  the  white  oxide  of  phosphorus  in  this 
experiment  ? 

C.     Action  of  Undiluted  Oxygen  Gas  on  Carbon. 

Proceed  as  in  B,  but  use  a  lump  of  charcoal  weigh- 
ing about  lg  instead  of  the  phosphorus.  Get  the  char- 
coal well  on  fire  by  heating  it  with  a  Bunsen  burner 

1  If  the  bottom  of  the  deflagrating  spoon  is  too  thick,  the  filings  will 
not  become  heated  enough  by  the  Bunsen  burner  before  they  are 
coated  with  oxide,  and  in  this  case  the  experiment  will  be  a  failure. 


OXYGEN.  19 

and  seal  the  jar  as  soon  as  possible.  Why  ?  Do  not  use 
a  deflagrating  spoon  that  has  any  phosphorus  in  it. 
Test  the  spoon  by  holding  it  a  minute  in  the  Bunsen 
flame. 

A  pretty  effect  may  be  obtained  if  a  little  powdered 
charcoal  is  sprinkled  over  the  lump  of  charcoal. 

If  on  opening  the  jar  under  water  the  oxygen  does 
not  appear  to  have  been  used,  test  the  remaining  gas 
with  a  glowing  match.  Give  the  chief  properties  of 
oxide  of  carbon.  This  addition  of  oxygen  to  another 
substance  is  called  oxidation.  The  term  is  also  some- 
times applied  to  the  addition  of  other  substances. 


Experiment  7. 
Preparation  of  Oxygen  from  Water. 

Have  ready  some  water  in  a  suitable  vessel 1  into 
which  pass  two  platinum  electrodes  s'o  arranged  that 
the  electric  current  in  passing  from  one  electrode  to  the 
other  must  pass  through  the  water.  Pass  a  current  of 
electricity  through  the  water  from  one  electrode  to  the 
other.  If  the  resistance  of  the  water  to  the  passage  of 
the  electric  current  is  too  great  for  a  rapid  evolution  of 
gas,  add  a  little  sulphuric  acid.  In  some  way  the  acid 
greatly  helps  the  current  to  get  through  the  water. 
Fill  a  small  tt  with  water.  Place  your  thumb  over  the 
mouth  of  the  tt,  and  invert  the  tube  over  the  electrode 
that  is  giving  off  the  gas  the  slower.  Catch  a  tt  of  the 
gas.  Do  not  let  any  of  the  other  gas  get  in.  Test  the 

i  See  Appendix  A. 


20  HYDROGEN. 

contents  of  the  tt  [glowing  match  test],  and  compare 
with  the  gas  got  from  the  air  [see  Ex.  1,  B  and  Ex. 
2,  B]  ;  also  with  the  gas  from  red  oxide  of  mercury 
[see  Ex.  5,  A].  Give  all  the  properties  you  can  of 
oxygen. 

Experiment  8. 

Examination  of  that  Constituent  of  Water  which  is 
not  Oxygen. 

Again  pass  the  electric  current  through  water,  as  in 
Ex.  7.  This  time  collect  the  gas  which  is  given  off  in 
larger  quantity.  Catch  a  tt  full.  Test  this  with  a 
glowing  match,  still  holding  the  tt  upside  down.  Why 
upside  down  ?  Answer  this  after  doing  Ex.  9,  B.  Is 
the  gas  oxygen  ?  If  not  found  to  be  oxygen,  test  at 
once  with  a  flaming  match.  Again  catch  some  of  the 
gas,  —  about  two-sevenths  of  a  tt  this  time.  Carefully 
let  the  air  fill  the  rest  of  the  tube.  Put  your  thumb 
over  the  end,  and  shake  to  mix  the  air  with  the  gas. 
Now  apply  quickly  a  lighted  match.  What  takes 
place  chemically  ?  Let  us  call  this  new  gas  hydrogen. 


Experiment  9. 

A.     The  Preparation  of  Hydrogen  from  Water  by  Means 
of  Iron. 

Note.  Ex.  1,  B,  taught  us  that  iron  when  hot  has 
attraction  for  oxygen.  If  water  [best  in  the  form 
of  steam]  is  passed  over  red-hot  iron  the  iron  will 
decompose  the  water,  take  the  oxygen  to  itself  and 


HYDROGEN.  21 

leave  hydrogen.  What  must  then  happen  to  the 
iron  ?  Proceed  as  follows,  and  see  if  your  inference  as 
to  the  answer  to  this  question  is  confirmed  by  experi- 
ment. Take  a  piece  of  half -inch  gas  pipe  about  two 
feet  long  with  a  one-hole  cork  in  each  end.  Put  about 
30g  of  iron  filings1  in  the  gas  pipe,  as  near  the  middle 
as  possible,  but  be  sure  there  is  a  passage  through  the 
whole  tube.  Clamp  the  gas  pipe  to  a  stand  at  each 
end.  Heat  the  filings  by  means  of  two  Bunsen  burners 
directed  at  the  same  point  on  the  gas  pipe.  Fit  your 
wash-bottle  flask  with  a  one-hole  cork  and  delivery 
tube.  Set  the  flask  on  a  tripod  stand  on  which  is  a 
piece  of  fine  iron  gauze  about  four  inches  square,  to 
prevent  the  bottom  of  the  flask  being  unevenly  heated. 
Put  some  water  in  the  flask,  set  a  Bunsen  burner 
below,  generate  steam  and  pass  the  steam  over  the  hot 
filings.  Have  a  delivery  tube  passing  from  the  filings 
down  into  the  pneumatic  trough.  Let  all  corks  be 
tight.  Catch  several  tts  of  the  gas  evolved.  Do  not 
try  to  keep  it  corked  up,  but  catch  the  gas  when  you 
need  it  for  the  following  work.  Reject  the  first  two 
tubefuls  because  there  is  apt  to  be  air  in  them. 

Caution  !  Caution  !  Caution  ! 

Hydrogen  and  air  form  an  extremely  dangerous  explo- 
sive mixture.  Use  the  utmost  care  in  all  work  with 
hydrogen.  Think  what  you  are  going  to  do  in  every  case 
before  you  act. 

Test  the  third  and  fourth  tubes,  as  you  tested  in  Ex. 
8,  to  prove  that  this  is  the  same  gas  we  agreed  to  call 

1  The  filings  should  be  as  free  as  possible  from  dirt  and  oil,  other- 
wise a  troublesome  smoke  may  appear. 


22  HYDROGEN. 

hydrogen.    Note  all  phenomena  as  you  test.      How  do 
you  explain  what  happens  when  you  apply  the  flame  ? 

What  shall  we  call  the  substance  that  results  when 
the  oxygen  of  the  air  joins  the  hydrogen,  causing 
the  intense  heat  and  fire  ?  What  is  the  common  name 
for  this  substance?  As  in  making  oxygen  from 
chlorate  of  potassium,  here  uncork  your  wash-bottle 
flask  before  you  stop  heating.  Why  ? 

B.     Specific  Gravity  of  Hydrogen. 

Catch  a  tt  of  hydrogen.  Put  your  thumb  over  the 
end  of  the  tube.  Remove  the  tube  from  the  trough. 
Hold  the  tube  upside  down.  Remove  the  thumb  care- 
fully. Wait  while  you  breathe  naturally  ten  times, 
i.e.,  wait  about  half  a  minute.  At  once  apply  a  flame 
to  the  tt's  mouth.  Again  catch  a  tt  full  and  proceed 
as  before,  but  now  hold  the  tt,  with  its  mouth  up, 
while  you  breathe  ten  times.  Again  catch  a  tt  full. 
Hold  a  second  tt  bottom  side  up  and  carefully  pour  the 
hydrogen  from  the  other  up  into  the  second.  At  once 
test  the  contents  of  the  second  for  hydrogen.  What 
do  you  say  in  regard  to  the  weight  of  hydrogen  ? 

C.     Action  of  Air  on  Warm  Hydrogen. 

Have  ready  an  eight-ounce,  wide-mouth  bottle  fitted 
with  a  two-hole  stopper.  Let  there  be  projecting 
up  straight  from  one  hole  a  piece  of  hard  glass  tube 
about  six  inches  long  with  one  end  just  reaching 
through  the  cork,  and  with  the  other  [upper]  end 
drawn  down  to  an  opening  about  like  the  tip  to  a  wash- 
bottle  nozzle.  Through  the  second  hole  of  the  cork  a 


SULPHUR.  23 

piece  of  common  glass  tube  should  be  inserted  reaching 
well  into  the  bottle  and  connecting  the  bottle  with  the 
hydrogen  gas  pipe.  This  bottle  serves  as  a  catch-bottle 
or  trap  to  condense  any  steam  that  gets  by  the  filings. 
It  best  be  set  in  a  dish  of  cold  water  or,  better,  in 
the  pneumatic  trough.  Generate  hydrogen  as  in  A,  but 
apply  the  blast  lamp  for  a  few  minutes  that  the  filings 
may  be  heated  red-hot  and  cause  a  good  flow  of  hydro- 
gen. As  there  is  some  danger  of  the  catch-bottle  blow- 
ing up,  apply  to  the  instructor l  for  a  method  of  testing 
the  explosive  quality  of  the  contents  of  this  bottle. 
When  all  is  safe,  light  the  hydrogen  as  it  issues  from 
the  small  jet,  and  let  it  burn  in  the  air.  What  is  the 
burning  ?  What  the  product  of  combustion  ?  Hold  a 
dry  and  cold  tt  over  the  jet.  Do  not  smother  the 
flame,  however.  Note  the  substance  that  forms  on  the 
sides  of  the  tt.  What  is  it  ? 


Experiment  1O. 

Sulphur. 

A.     The  Properties  of  Sulphur. 

Take  some  roll  brimstone,  and  some  flowers  of  sul- 
phur. Note  the  chief  properties  of  sulphur.  Review 
the  records  of  iron,  phosphorus,  mercury,  carbon, 
oxygen,  hydrogen,  and  all  the  oxides  you  have  made. 
Compare  sulphur  with  the  other  substances  you  have 
studied. 

1  See  Appendix  B. 


24  SULPHUB. 


B.     Modifications  of  Sulphur. 

1.  Dissolve  about  a  gram  of  roll  brimstone  in  about 
five    cc    of   sulphide  of  carbon   [one  of  the  very  few 
things    in    which    sulphur    will    dissolve].      Caution ! 
/Sulphide  of  carbon  is  very  volatile   and  inflammable. 
Have  no  fire  near.     Best  grind  the  sulphur  to  a  powder 
in  a  mortar  to  make  it  dissolve  quickly.     The  flowers 
do  not  dissolve  as  well  as  the  roll.     Pour  the  solution 
out  in  a  crystal  pan,1  and  let  the  sulphide  of  carbon 
evaporate  spontaneously.     Examine  the  form  and  color 
of  the  crystals  deposited. 

2.  Melt  enough  roll  brimstone  to  fill  a  small  common 
beaker  nearly  full.     In  melting  the  sulphur,  the  beaker 
should  be  set  on  iron  gauze  or  asbestos-  paper.     If  the 
sulphur  in  the  beaker  catches  fire  turn  off  your  gas  and 
smother  the  fire  with  an  inverted  dish  or  a  cloth.    Take 
care  that  the  temperature  does  not  rise  much  above  the 
melting  point  of  the  sulphur.     Let  the  sulphur  cool  till 
crystals  begin  to  shoot  across  the  surface  and  just  meet 
in  the  middle,  then  promptly  pour  out  into  water  what 
remains   liquid.      Note    the    form    and    color    of    the 
crystals  left  in  the  beaker.     Compare  with  those  of  1. 

3.  Melt  some  sulphur  in  a  tt.     Hold  the  tt  over  a 
naked  Bunsen  flame.2     Raise  the  temperature  till  the 
substance,  after  it  melts  to  a  liquid,  becomes  thick  and 
viscous.     What  is  meant  by  viscous?     Then  pour  the 
sulphur  out  in  a  fine  stream  into  cold  water.     Note  the 
form  of  the  sulphur  in  the  water.     Compare  sulphur 

1  A  shallow  glass  dish. 

2  See  Manipulations  for  method  of  holding  a  hot  tt. 


SULPHITE.  25 

with  carbon,  phosphorus,    etc.,  in  regard  to  allotropy. 
What  is  allotropy  ? 

C.     Action  of  Oxygen  on  Hot  Sulphur. 

Prepare  more  oxygen  in  .the  following  manner. 
Take  12g  chlorate  of  potassium  and  mix  with  it  3g  of 
powdered  black  oxide  of  manganese.1  The  black  oxide 
should  be  mixed  intimately  with  the  chlorate.  Do  not 
spill  any.  Heat  the  mixture  in  a  Kjeldahl  flask  as  in 
Ex.  5,  B.  Do  not  use  here  a  pneumatic  trough  filled 
with  water,  for  collecting  the  gas,  but  fill  three  or  four 
dry  jars  by  displacement,  i.e.,  pass  the  delivery  tube 
[best  have  one  ending  in  about  15cm  rubber  tube,] 
directly  into  the  jar.  Hold  the  cover  on  as  well  as 
possible.  The  oxygen  gas,  which  is  somewhat  heavier 
than  air,  will  collect  at  the  bottom  of  the  jar  and  push 
the  air  up  and  out.  You  can  tell  when  the  jar  is  full 
by  holding  a  glowing  match  at  the  crack  left  between 
the  cover  and  the  edge.  When  the  jar  is  full,  with- 
draw the  rubber  tube  slowly  that  the  oxygen  may  fill 
the  space  occupied  by  the  tube.  Snap  on  the  cover  at 
once.  Set  away,  for  the  next  experiments,  at  least  two 
jars  that  seem  perfectly  dry.  Do  not  throw  away  the 
contents  of  the  Kjeldahl  flask,  but,  when  cool,  add 
about  100CC  of  warm  water.  The  white  chloride  of 
potassium  dissolves,  while  the  black  oxide  of  manganese 
does  riot.  Take  a  funnel  and  a  filter  paper 2  to  fit  the 
funnel.  Pour  the  contents  of  the  flask  on  the  filter 

1  The  black  oxide  of  manganese  of  trade  is  sometimes  adulterated 
with  coal  dust.      Such  adulteration  might  cause  a  serious  explosion  in 
this  experiment.     Why? 

2  For  directions  about  filter  papers,  see  Manipulations. 


26  SULPHUR. 

paper.  By  means  of  the  wash-bottle  pass  about  100CC 
of  water  through  the  black  oxide  of  manganese  to  carry 
through  the  chloride  of  potassium.  Dry  the  black 
oxide  and  weigh  it.  In  order  to  dry  the  black  oxide, 
have  ready  a  weighed  porcelain  evaporating  dish. 
Transfer  the  black  oxide  to  this  dish,  using  a  fine 
stream  from  the  wash-bottle  to  wash  the  last  traces  of 
the  oxide  into  the  dish  while  you  hold  the  paper  just 
above  the  dish.  Evaporate  off  the  water,  avoiding  all 
spattering,1  and  with  a  small  flame  dry  the  black  oxide 
in  the  dish  to  constant  weight.  In  drying,  never 
allow  the  black  oxide  to  be  heated  to  redness.  Why? 
To  dry  a  substance  to  constant  weight,  heat  it  until  it 
seems  dry,  then  Aveigh  it,  again  heat  it,  weigh  again, 
and  if  the  weight  is  the  same  as  that  previously  found 
no  further  drying  is  necessary.  If  there  has  been  a  loss 
after  the  second  heating,  again  heat,  weigh  and  so  con- 
tinue till  no  further  loss  in  weight  is  found.  You 
should  have  the  same  amount  of  black  oxide  that  you 
started  with,  i.e.,  3g. 

Note.  This  black  substance  is  the  oxide  of  the  metal 
manganese.  Compare  it  with  the  oxide  of  iron  you 
made.  We  do  not  know  its  action  in  this  experiment, 
but  it  certainly  makes  the  oxygen  come  off  easily. 
What  do  you  think  of  its  action  ?  Compare  the  use  of 
sulphuric  acid  when  you  decomposed  water  with  the 
electric  current. 

1  Spattering  is  best  avoided  by  evaporating  at  such  a  low  tempera- 
ture that  the  liquid  does  not  actually  boil.  Best  set  the  evaporating 
dish  over  a  beaker  containing  water  which  is  kept  boiling  by  a 
Bunsen  burner  beneath.  This  method  of  slow  evaporation  is  called 
"  Evaporation  over  the  water-bath." 


SULPHUROUS    ACID.  27 

Burn  a  small  piece  of  sulphur  on  a  clean  deflagrating- 
spoon  in  a  jar  of  oxygen.  Open  under  water,  note  the 
condition  of  the  jar,  and  at  once  snap  on  the  cover 
again.  If  no  water  has  entered  the  jar,  let  in  about 
50CC.  Shake  with  the  water  that  has  entered.  Again 
open  under  water  and  note  the  condition  of  the  jar. 
Note  the  properties  of  the  new  compound  formed, 
especially  its  state,  color,  odor,  and  solubility  in  water. 
What  shall  we  call  the  new  compound?  Will  it 
weigh  more  than  the  original  oxygen? 


Experiment  11. 

Sulphurous  Acid. 

Again  burn  sulphur  in  a  jar  of  oxygen.  Do  not  open 
under  water,  but  remove  the  spoon  carefully,  and  add 
about  20CC  of  water.  Shake  well.  Try  -the  effect  of 
the  liquid  on  a  bit  of  blue  litmus  paper.1  Try  the 
effect  of  water  itself  on  the  same  kind  of  test  paper. 
Taste  a  very  small  amount  of  the  new  liquid.  Let  us 
call  our  new  substance  sulphurous  acid.  What  three 
simple  substances  must  there  be  in  this  acid? 


Experiment  12. 
A  Second  Oxide  of  Sulphur. 

Oxygen  may  be  made  to  join  the  gaseous  oxide  of 
sulphur  and  form   a  second  oxide   of  sulphur.     Have 

1  For  the  preparation  and  use  of  litmus  paper  see  Appendix  C. 


28  OXIDE   OF   SULPHUR. 

ready  weighed  in  a  clean  and  dry  defiagra ting-spoon 
just  0.3g  of  sulphur.  Burn  the  sulphur  as  in  Ex.  11, 
but  do  not  remove  the  spoon.  The  0.3g  of  sulphur  are 
not  enough  to  use  all  the  oxygen.  Therefore  you  have 
in  the  jar,  after  the  burning,  oxygen  and  oxide  of 
sulphur.  What  are  the  properties  of  oxygen,  —  of 
oxide  of  sulphur  ?  Have  ready  a  suction  pump  l  and  a 
tube  of  hard  glass  containing  a  little  platinum  sponge, 
or  platinized  asbestos.2  This  tube  containing  the  plati- 
num should  be  15-20cm  long  and  have  a  bore  of  about 
6min.  The  platinum  sponge,  or  asbestos,  should  not  be 
packed  so  tightly  that  the  gases  cannot  easily  pass 
through.3  Also  have  ready  a  piece  of  glass  tube  bent 
in  the  form  of  a  U,  the  total  length  of  this  tube  to  be 
about  40cm.  One  end  of  this  tube  should  be  connected 
with  the  platinum  sponge  tube,  and  the  other  with  the 
suction  pump  —  each  by  a  piece  of  rubber  as  short  as 
possible,  for  the  oxide  formed  corrodes  rubber.  Place 
the  U-tube  in  a  freezing  mixture.4  Suck  dry  air  through 
the  whole  apparatus,  slowly,  for  five  minutes,  to  remove 
all  moisture.  The  air  may  be  dried  by  connecting  the 
platinum  sponge  tube  with  two  catch-bottles5  of  sul- 
phuric acid.  Heat  the  platinum  sponge  well  with  a 
Bunsen  burner.  The  sponge  tube  may  best  be  sup- 
ported by  a  stand  and  wire  gauze.  As  soon  as  the 

1  For  the  use  of  the  suction  pump  see  Appendix  D. 

a  O.IK  of  platinized  asbestos  is  sufficient,  but  0.2  are  better. 

8  It  is  well  to  insert  within  the  hard  glass  tube  two  bits  of  small 
soft  glass  tube  —  one  on  each  side  of  the  platinum — in  order  to  pre- 
vent the  platinum  being  driven  out  by  any  sudden  puff  of  gases. 

4  Crushed  ice  or  snow,  salt,  and  enough  water  to  make  a  pasty  mass, 
are  good  for  a  freezing  mixture. 

6  See  Appendix  E. 


SULPHURIC   ACID.  29 

sponge  is  hot,  and  the  whole  apparatus  dry,  disconnect 
the  catch-bottles,  fit  a  piece  of  rubber  tube  about  15cm 
long  to  that  end  of  the  platinum  sponge  tube  from 
which  the  catch-bottles  were  removed,  pass  the  end  of 
this  rubber  tube  to  the  bottom  of  the  jar  containing 
the  mixture  of  oxygen  and  the  gaseous  oxide  of  sul- 
phur, and  then,  using  the  hand  to  prevent,  as  far  as 
possible,  the  air  mixing  with  the  contents  of  the  jar, 
let  the  pump  slowly  suck  the  gases  from  the  fruit  jar, 
over  the  hot  platinum,  into  the  cooled  U-tube.  Look 
for  white  crystals  in  the  U-tube,  which  must  be  kept 
very  cold. 

If  you  should  weigh  the  platinum  sponge  before  the 
experiment  and  after,  you  would  find  no  change  in 
weight.  The  sponge  itself  does  not  make  any  part  of 
the  crystals.  From  what  must  the  crystals  be  made? 
Remove  the  crystals  from  the  cold  bath  and  examine 
them  before  they  melt.  Let  us  call  this  new  substance 
the  second  oxide  of  sulphur.  Keep  the  new  substance 
for  the  next  experiment. 


Experiment  13. 
Sulphuric  Acid. 

Compare  the  record  of  Ex.  11,  where  you  made  sul- 
phuroMS  acid.  Now  take  the  second  oxide  of  sulphur 
made  in  Ex.  12  [which  becomes  liquid  if  allowed  to 
stand  long  at  ordinary  temperature],  and  add  a  few 
drops  of  water  from  the  wash-bottle.  Try  the  effect 


30  SULPHURIC   ACID. 

of  the  resulting  liquid  on  blue  test  paper.  Dilute  more 
and  taste  of  a  very  little.  Let  us  call  our  new  acid 
sulphuric  acid.  What  three  things,  each  simple,  must 
there  be  in  sulphuric  acid?  In  what  respect  does 
sulphuric  acid  differ  from  sulphurous? 


Experiment  14. 

Removal  of  Hydrogen  from  Sulphuric  Acid. 

Take  a  small  flask  fitted  with  a  one-hole  cork  and 
a  delivery  tube  reaching  to  a  pneumatic  trough.  Pour 
about  10CC  of  water  into  the  flask.  Then  add  5CC  of 
sulphuric  acid.1  Caution!  Never  add  water  to  sul- 
phuric acid.  Add  the  sulphuric  acid  to  the  water. 
Sulphuric  acid  and  water  can  generate  great  heat.  If 
the  amount  of  acid  is  large  and  that  of  water  small, 
this  heat  may  boil  the  water  with  explosive  violence. 

Have  ready  about  10g  of  iron  [best  in  the  form  of 
small  nails].  Add  the  iron  to  the  flask  before  the 
liquid  has  had  time  to  cool,  and  insert  the  cork  with  its 
delivery  tube.  Caution!  Keep  all  fire  away.  Why? 
After  the  gas  has  passed  long  enough  to  drive  the  air 
from  the  flask,  catch  a  tt  of  it  and  test  it.  What  is  it  ? 
Prove  that  iron  has  not  the  power  of  removing  the 
hydrogen  from  water,  at  a  low  temperature,  by  putting 
some  nails  in  a  tt  and  warming  till  the  water  is  at 

1  When  the  student  has  once  made  a  compound  substance,  it  is  not 
supposed  that  he  is  to  make  enough  for  all  subsequent  work.  He 
should  be  supplied  with  the  commercial  article. 


SULPHATE    OF    IKON.  31 

least  as  warm  as  was  the  mixture  in  the  flask.  If 
the  hydrogen  did  not  come  from  the  10CC  of  water, 
whence  must  it  have  come  ?  What  has  happened  to 
that  part  of  the  sulphuric  acid  that  was  made  of  sulphur 
and  oxygen?  Answer  this  question  by  experiment, 
as  follows : 

Put  the  contents  of  the  flask  in  an  evaporating  dish. 
Add  about  25CC  of  water.  Set  the  dish  on  tripod  or 
ring,  and  warm  gently  till  no  more  hydrogen  is  given 
off.  [While  warming,  keep  the  volume  of  the  liquid 
as  nearly  constant  as  possible  by  adding  water  if  any 
evaporates  off.]  Filter  and  evaporate  the  liquid  till  a 
little  of  it,  when  taken  out  in  a  tt  and  cooled,  will 
deposit  crystals.  Then  at  once,  while  still  hot,  again 
filter  the  liquid  into  a  beaker.  Hold  the  beaker  so  that 
cold  water  shall  flow  over  the  outside  till  the  liquid 
within  is  cold.  Note  the  crystals  formed.  Filter, 
spread  the  crystals  on  paper  to  dry.  Note  their  prop- 
erties. Let  us  call  the  new  substance  sulphate  of  iron. 
The  green  crystals  are  made  of  sulphate  of  iron  and 
water  of  crystallization,  i.e.,  water  which  is  in  some 
way  joined  to  the  sulphate  of  iron.  Many  substances 
in  this  way  form  crystals  by  the  addition  of  water. 
Put  some  of  the  green  crystals  in  a  dry  tt  and  heat 
over  a  Bunsen  burner.  Note  the  formation  on  the 
sides  of  the  tt.  What  forms  there?  Of  what  simple 
substances  do  you  say  sulphate  of  iron  is  composed? 
Of  what  compound  substances  were  the  green  crystals 
composed? 

Iron  is  a  simple  substance,  and  sulphuric  acid,  we 
have  proved^  contains  hydrogen,  sulphur,  and  oxygen. 


32  OXIDE   OF   IRON   WITH   WATER. 

The  mutual  action  of  iron  and  sulphuric  acid  may  be 

iron      hydrogen  . 

represented  by  a  diagram,  thus:  '  sulpliur  1ms 

oxygen 

indicates  that  the  iron  has  changed  place  with  the  hydro- 
gen of  the  acid,  i.e.,  the  hydrogen  has  become  free,  and 
the  iron  has  become  combined  with  the  sulphur  and 
oxygen  that  were  in  the  acid,  making  a  new  substance 
—iron  sulphate — whose  composition  may  be  repre- 

firon        "I 

sented  thus :     sulphur  . 

loxygen  j 

Remembering  that  water  is  oxide  of  hydrogen,  i.e., 
hydrogen  -f  oxygen,  we  may  represent  the  formation  of 
the  green  crystals  thus  : 

iron 

sulphur 

oxygen 

hydrogen 
oxygen 

Note.  We  have  already  proved  that  sulphuric  acid 
contains  more  than  one  portion  of  oxygen:  hence 

"oxygen"  in  our    Uuip^ur    |  stands  for  the  total  amount 

(^oxygen     J 

of  oxygen  present  in  the  acid.  How  have  we  proved  that 
there  is  more  than  one  portion  of  oxygen  in  sulphuric  acid? 


asar  +        .  g^es  <°r=) 


Note.  Having  found  that  water  added  to  either 
oxide  of  sulphur  forms  an  acid,  it  becomes  of  interest 
to  see  if  water  can  form  an  acid  with  any  other  oxide 
except  the  oxides  of  sulphur. 

Experiment  15. 
Action  of  Water  on  Oxide  of  Iron. 

Add  a  little  water  to  the  oxide  of  iron  made  in  Ex.  6,  A. 
Test  with  litmus  paper.  Has  an  acid  been  formed  ? 


OXIDES    WITH   WATER.  33 

Experiment  16. 

Action  of  Water  on  Oxide  of  Phosphorus. 

Again  prepare  some  oxide  of  phosphorus,  by  burning 
a  small  amount  of  phosphorus  in  a  dry  jar  of  air,  or, 
better,  oxygen.  To  the  oxide  add  about  10CC  of  water. 
Shake.  Test  the  properties  of  the  resulting  liquid. 
Taste  of  a  drop.  How  many  and  what  simple  sub- 
stances have  been  used  in  the  preparation  of  phosphoric 
acid?1 


Experiment  17. 

Action  of  Water  on  Oxide  of  Carbon. 

Again  prepare  some  oxide  of  carbon.  Be  sure,  by 
testing,  that  all  vessels  used  in  this  experiment  are 
free  from  sulphuric  acid.  To  the  jar  containing  the 
oxide  of  carbon  add  about  10CC  of  water.  Shake  well. 
Test  the  resulting  liquid  both  by  litmus  and  by  taste. 
Compare  its  acid  properties  with  those  of  the  other 
acids  you  have  made.  Which  acid  has  the  most  marked 
acidity?  Which  the  least?  Let  us  call  the  acid  sub- 
stance made  in  this  experiment  carbonic  acid.  What 
simple  substances  make  up  carbonic  acid?  Place  the 
carbonic  acid  in  a  small  beaker  and  warm.  What 
happens?  Finally  bring  the  liquid  just  to  a  boil. 
Test  the  liquid  remaining  in  the  beaker  with  litmus. 

1  Phosphorus  is  capable  of  forming  several  acids  :  the  one  made  here 
is  commonly  called  metaphosphoric  acid. 


34  ZINC. 


What  is  the  liquid  left?  Are  the  component  parts  of 
carbonic  acid  bound  together  strongly  or  not?  What 
are  the  component  parts  of  carbonic  acid? 


Experiment  18. 

Zinc. 

A.     The  Properties  of  Zinc. 

Take  some  zinc, — sheet,  granular,1  and  dust.  Get 
the  chief  properties  of  this  substance. 

B.     Oxidation  of  Zinc. 

Put  a  few  grams  of  zinc  in  a  small  Hessian  crucible. 
Heat  over  the  blast-lamp  till  the  zinc  melts.  Continue 
the  heating,  with  an  occasional  stir  by  means  of  an 
iron  rod,  till  the  zinc  burns.  What  is  the  burning 
chemically?  Examine  the  product  of  the  combustion, 
which  sometimes  forms  what  is  called  Philosophers' 
Wool.  Get  the  properties  of  oxide  of  zinc,  especially 
its  color  when  hot — when  cold.  Save  some  zinc  oxide 
[free  from  zinc]  for  C.  Having  found  that  many  oxides 
with  water  form  acids,  it  becomes  interesting  to  add 
water  to  every  new  oxide  we  make. 

C.     Action  of  Water  on  Oxide  of  Zinc. 

Take  a  little  of  the  zinc  oxide  made  in  B,  put  it  in  a  tt 
and  add  water.  Note  effect.  Test  the  liquid  with  litmus, 

1  Granular  ainc  [the  most  convenient  form  for  general  chemical 
use]  may  be  made  by  melting  any  form  of  zinc  in  a  ladle,  Hessian 
crucible,  or  other  suitable  vessel,  and  pouring  the  molten  metal  from 
a  height  into  a  vessel  of  water. 


A   SECOND   OXIDE   OF   CARBON.  35 

particularly  with  litmus  that  has  been  turned  slightly  red 
by  a  weak  acid,  as  carbonic.  Compare  [and  state  the 
result  of  comparison]  the  action  of  water  on  oxide  of 
zinc  with  action  of  water  on  other  oxides  you  have  tried. 


Experiment  19. 

Action  of  Zinc  on  the  Non-combustible  Oxide  of 
Carbon;  or, 

Preparation  of  a  Second  Oxide  of  Carbon. 

Have  ready  a  piece  of  large,  hard  glass  tube  about 
20cm  long.  Put  in  the  midst  of  this  tube  four  or  five 
grams  of  zinc  in  the  form  of  zinc  dust.1  Also  have 
ready  a  rubber  bag  nearly  filled  with  the  non-combustible 
oxide  of  carbon.2  Clamp  the  glass  tube  with  its  charge 
of  zinc  at  a  convenient  height  for  heating  the  zinc  with 
a  Bunsen  burner.  Fit  an  empty  gas  bag  to  one  end  of 
the  tube  and  the  bag  containing  the  oxide  of  carbon  to 
the  other.  Heat  the  zinc  and  slowly  pass  the  gas  from 
bag  to  bag  for  a  few  minutes.  Note  the  formation  of 
oxide  of  zinc — yellow  when  hot,  white  when  cold. 
Whence  came  the  oxygen  to  form  oxide  of  zinc?  Does 
the  resulting  gas  occupy  as  much  space  as  the  original 
gas?  Remove  the  bag  from  the  tube  without  letting 
any  of  the  gas  escape.  Fit  a  cork,  through  which 
passes  a  short  piece  of  glass  tube,  ending  in  about  15cm 

1  The  zinc  dust  should  be  in  the  form  of  a  very  fine  powder. 

2  This  gas  should  be  prepared  by  the  instructor  and  given  to  the 
student  whenever  needed  up  to  the  time  of  doing  the  experiment  in 
which  the  student  learns  the  action  of  an  acid  on  marble.     For  a 
method  for  preparing  this  gas  on  a  large  scale,  see  Appendix  F. 


36  REDUCTION. 

rubber  tube,  to  the  mouth  of  the  rubber  bag.  Catch  a 
small  bottle,  e.g.,  a  two-ounce  salt-mouth  bottle,  full  of 
the  gas  over  the  pneumatic  trough.  Do  not  use  more 
than  one  half  of  all,  as  some  must  be  saved  for  Ex.  20. 
Set  fire  to  the  new  gas  in  the  bottle.  Have  a  dark  back- 
ground, as  the  new  gas  will  burn  with  only  a  pale  flame, 
Note  the  color  of  the  flame.  Caution  !  Do  not  breathe 
any  of  this  gas,  as  it  is  a  vigorous  poison.  What  are 
the  chief  properties  of  this  new  gas  ?  Compare  it  espe- 
cially with  the  gas  from  which  it  was  made.  What  do 
you  consider  the  new  gas  to  be  ?  How  formed  ?  How 
distinguished  from  the  first  gas  you  made  from  carbon  ? 
This  taking  away  of  oxygen  [or  any  similar  substance] 
from  another  substance  is  called  reduction.  Reduction 
is  the  opposite  of  oxidation.  Mention  several  cases  of 
oxidation  we  have  already  had.  Mention  several  of 
reduction,  and  tell  in  each  of  the  latter  by  what  means 
the  reduction  was  accomplished. 

Note.  If  the  non-combustible  oxide  of  carbon  did  not 
contain  at  least  two  parts  of  oxygen  what  would  be  left 
in  the  bags  when  the  zinc  had  taken  to  itself  one  part 
of  oxygen  to  form  the  zinc  oxide  that  you  saw  in  the 
tube  ?  What  was  left  in  the  bags  ?  Are  we  not  justi- 
fied, then,  in  writing  the  non-combustible  oxide  as  if  it 
contained  a  double  portion  of  oxygen?  Let  us  here- 
after call  this  oxide  the  dioxide  of  carbon.1 

The  chemical  change  brought  about  in  this  experi- 
ment may  be  represented  by  a  diagram,  thus  : 


1  The  old-fashioned  name  for  this  oxide  is  carbonic  acid.    It  is  not, 
however,  an  acid. 


OXIDATION.  B7 

Experiment  2O. 
Oxidation  of  the  Combustible  Oxide  of  Carbon. 

Have  ready  in  a  short,  e.g.,  25cm,  piece  of  combustion 
tube1  a  small  amount  of  the  red  oxide  of  mercury. 
Attach  an  empty  rubber  bag  to  one  end  of  the  tube  and 
a  bag  containing  the  combustible  oxide  of  carbon,  made 
in  Ex.  19,  to  the  other  end.  Heat  the  oxide  of  mercury 
gently  with  a  single  Bunsen  burner,  and  slowly  pass  the 
gas  from  end  to  end.  Note  the  effect  on  the  oxide  of 
mercury.  When  no  further  effect  is  visible,  cease  passing 
the  gas  and  test  for  the  combustible  oxide  of  carbon,  then 
for  the  non-combustible.  Use  the  flame  test.  How  do 
you  explain  the  change  that  has  taken  place  ?  Draw  a 
diagram  that  will  show  the  change.  Let  us  hereafter 
call  this  combustible  oxide  the  monoxide  of  carbon.2 

Note.  When  charcoal  instead  of  zinc  is  used  in 
Ex.  19,  there  result  from  the  one  bag  of  the  carbon 
dioxide  two  bags  of  the  carbon  monoxide.  Explain 
this  doubling  of  volume.  If  these  two  volumes  of 
carbon  monoxide  should  be  passed  over  hot  oxide  of 
mercury  how  many  volumes  of  carbon  dioxide  would 
result  ? 


Experiment  21. 

Action  of  Zinc  on  Sulphuric  Acid. 

Make  an  experiment  parallel  to  Ex.  14,  but  use  zinc, 
best  in  the  granular  form,  where  you  there  used  iron. 

1  Hard  glass  tube,  with  a  bore  of  10-20mm. 

2  Carbon  monoxide  is  also  called,  correctly,  carbonous  oxide.     Com- 
pare the  names  of  sulphurous  and  sulphuric  oxides  and  acids. 


38 


FACTORS   AND   PRODUCTS. 


Be  sure  you  omit  no  part  of  the  experiment.  Of  what 
simple  substances  are  the  crystals  composed?  Note. 
This  experiment  teaches  you  one  of  the  best  ways 
known  for  making  large  quantities  of  a  certain  gas. 
What  gas  ?  Draw  diagrams  to  show  the  changes. 
Compare  the  diagram  of  Ex.  14. 


Experiment  22. 
Action  of  Oxide  of  Zinc  on  Sulphuric  Acid. 

Proceed  as  in  Ex.  21,  but  here  use  oxide  of  zinc. 
Be  sure  you  note  how  the  oxide  behaves  when  put  into 
pure  water  as  well  as  when  put  into  water  and  sul- 
phuric acid.  Why  is  hydrogen  not  given  off  in  this 
experiment  as  in  Ex.  21  ?  State  what  has  happened 
chemically  in  this  [22d]  experiment.  Also  state  the 
products  of  the  chemical  change.  What  were  the 
factors  of  the  chemical  change?  What  simple  sub- 
stances combined  made  each  factor  ?  What  simple  sub- 
stances combined  make  each  product?  What  is  a 
chemical  factor,  —  what  a  product  ? 

Note  that  a  diagram  like  the  following  will  not  only 
show  the  simple  substances  in  both  factors  and  prod- 
ucts, but  will  express  the  chemical  change  that  has 
taken  place. 


zinc 


oxy. 

A 


hyd.        < 


oxy. 
sul. 


SULPHIDE   OF   IRON.  89 

Experiment  23. 
Sulphides. 

A.     Mutual  Action   of  Iron  and  Sulphur,   when  warmed ;  or, 
Formation  of  Sulphide  of  Iron. 

Take  about  one-half  a  cc  of  iron  filings  and  an 
equal  volume  of  flowers  of  sulphur.  Mix  well,  then 
heat  well  in  a  large  bulb  tube *  or  in  a  tt.  Break  the 
tube  and  examine  the  substance  formed.  Let  us  call 
this  sulphide  of  iron.  Get  its  chief  properties. 
Express  the  change  thus  :  iron  +  sulphur  =  sulphide 
of  iron  ;  or  thus  :  iron  +  sulphur  =  [g^11]. 

B.     Action  of  Hydrogen  on  Warm  Sulphur ;  or, 
Formation  of  Sulphide  of  Hydrogen. 

Generate  hydrogen  as  follows  :  Place  in  a  250CC  flask 
about  100CC  of  water  and  about  20CC  of  sulphuric  acid. 
Add  about  30g  granular  zinc.  Have  ready  a  tt,  with 
about  10g  sulphur  [best  in  the  form  of  roll  brimstone] 
in  it ;  also  a  tube  to  connect  the  hydrogen  flask  with 
the  tt,  so  that  hydrogen  can  be  conducted  two  thirds 
of  the  way  down  into  the  tt  of  sulphur.  The  sulphur 
tt  should  be  fitted  with  a  two-hole  cork.  Through  one 
hole  of  this  cork  enters  the  hydrogen  tube,  which 
passes  two  thirds  of  the  way  down  into  the  tt ;  through 
the  second  hole  of  the  cork  passes  out  an  exit  tube. 
The  exit  tube,  made  of  hard  glass,  should  start  even 
with  the  lower  surface  of  the  cork,  pass  up  through 
the  cork,  then  be  bent  at  a  right  angle.  Toward  its 
1  Same  as  Matrass  of  Ex.  5,  A. 


40  StTLMlbti  OF 


outer  end  the  exit  tube  should  be  drawn  down  to  a 
capillary  tube  and  turned  up  at  a  right  angle  in  the 
midst  of  this  capillary  part.  The  capillary  part  should 
have  a  total  length  of  not  less  than  10cm.  Caution  ! 
Pass  tne  hydrogen  till  safe  to  light  it  at  the  tip  of  the 
capillary  tube.  Prove  that  all  is  safe  by  the  explosion 
tube^  as  in  Ex.  9,  C.  Then  boil  the  sulphur  till  the 
vapor  of  the  sulphur  nearly  fills  the  tt.  If  the  hydro- 
gen is  still  burning,  blow  out  the  flame.  Note  the  odor 
of  the  new  gas  coming.  Let  us  call  this  new  substance 
sulphide  of  hydrogen.  Of  what  must  sulphide  of 
hydrogen  be  composed  ?  Place  a  Bunsen  burner  flame 
under  the  exit  tube  just  before  it  is  narrowed  to  the 
capillary  part.  What  is  the  deposit  in  the  capillary 
part  ?  What,  then,  must  be  going  off  ?  Light  the  jet 
and  see  if  your  answer  to  the  last  question  is  correct. 
Express  all  the  chemical  actions  in  the  form  of  equa- 
tions in  a  manner  similar  to  that  indicated  for  Part  A 
of  this  experiment. 

C.     Action  of  Sulphuric  Acid  on  Sulphide  of  Iron. 

State  the  simple  substances  that  have  gone  to  make 
up  each  of  these  compounds.  Put  in  a  250CC  flask  50CC 
water  and  15CC  sulphuric  acid.  Warm  somewhat. 
Then  put  in  25g  sulphide  of  iron.  When  the  action 
begins  catch  in  a  dry  fruit  jar  some  of  the  gas  formed. 
Catch  by  displacement.  How  do  you  catch  by  dis- 
placement? Do  not  warm  after  the  sulphide  of  iron 
has  been  added.  What  is  the  gas  formed?  Test  a 
jarful  by  the  flame  test.  What  are  deposited  on  the 
sides  of  the  jar?  What  is  left  in  the  jar  after  the 


41 

fire?  Tell  by  the  odor.  How  must  this  have  been 
formed?  Get  the  properties  of  sulphide  of  hydrogen, 
particularly  odor  and  solubility.  This  gas  is  often 
called  sulphuretted  hydrogen.  In  this  experiment 
what  has  happened  to  the  sulphide  of  iron  and  to  the 
sulphuric  acid?  Answer  this  question  after  doing  as 
follows :  Transfer  the  contents  of  the  flask  to  a  porce- 
lain evaporating  dish.  Evaporate  with  a  very  gentle 
heat  till  a  little  of  the  liquid  taken  out  and  cooled  will 
deposit  crystals.  Immediately  filter  the  contents  of 
the  dish.  Cool  the  liquid  which  runs  through  and 
examine  the  crystals  deposited.  What  are  these 
crystals  ? 

Draw  a  diagram  which  will  show  the  simple  sub- 
stances in  both  the  factors  and  the  products,  and  will 
indicate  the  chief  chemical  change. 


Experiment  24. 

Copper. 
A.     The  Properties  of  Copper. 

Take  some  sheet  copper  and  some  copper  wire.  Get 
the  chief  properties  of  copper,  as  color,  lustre,  hard- 
ness, tenacity,  etc. 

B.     Oxidation  of  Copper. 

Take  small  pieces  of  copper  wire.  Proceed  just  as 
in  Ex.  1,  B,  but  use  copper  instead  of  iron.  What 
shall  we  call  the  black  coating  formed  on  the  bits  of 
wire  ?  Get  the  chief  properties  of  this  new  substance. 


42  COPPER. 

Save  some  for  C.     How  much  oxygen  gas  was  taken 
from  the  air  in  this  experiment? 

C.    Reduction  of  the  Black  Oxide  of  Copper  to  Copper. 

Take  the  black  oxide  of  copper  made  in  B.  Place 
this  in  a  piece  of  hard  glass  tube.  The  tube  best  be 
drawn  out  and  turned  up,  as  in  the  hydrogen  sulphide 
experiment.  Generate  hydrogen  as  in  Ex.  23.  When 
it  is  desirable  to  generate  a  constant  stream  of  hydro- 
gen, it  is  well  to  have  a  thistle  tube  as  well  as  a  delivery 
tube  passing  through  the  cork  of  the  generating  flask. 
The  lower  end  of  the  thistle  tube  should  pass  nearly  to 
the  bottom  of  the  flask.  Why?  Through  the  thistle 
tube  portions  of  a  mixture  of  one  volume  of  sulphuric 
acid  to  five  of  water  can  be  poured  from  time  to  time 
as  the  action  lessens.  In  this  way  no  air  is  admitted, 
as  there  would  be  if  the  stopper  should  be  taken  out 
and  the  acid  solution  poured  in.  Caution !  Keep  all 
fire  away.  Why?  Dry  the  hydrogen  by  passing  it 
through  a  catch-bottle  of  sulphuric  acid.  Then  pass 
the  hydrogen  through  the  hard  glass  tube  and  over  the 
oxide  of  copper.  Test  with  explosion  tube.  When 
safe,  light  the  jet  of  hydrogen,  and  as  the  gas  passes, 
gently  heat  the  oxide  of  copper.  Note  the  phenomenon. 
Explain.  What  becomes  of  the  oxygen  that  was  united 
with  the  copper  forming  the  oxide  of  copper  ?  Examine 
your  apparatus  and  see  if  your  answer  to  the  last  ques- 
tion is  proved  correct.  What  is  left  where  copper 
oxide  was  ?  What  is  a  reduction  ?  What  is  oxidation  ? 
Contrast  reduction  and  oxidation. 

Draw  a  diagram  to  show  the  chief  chemical  change 
in  this  part  of  the  experiment. 


MAGNESIUM.  43 

Experiment  25. 
Magnesium. 

A.     Properties  of  Magnesium. 

Take  some  magnesium  in  the  form  of  ribbon  and 
powder.  Get  the  chief  properties  of  magnesium. 
Note  particularly  the  color,  lustre,  tenacity,  brittleness, 
and  weight. 

B.     Oxide  of  Magnesium. 

Make  this  substance.  Describe  your  method  of  prep- 
aration. Get  the  chief  properties  of  oxide  of  mag- 
nesium. Save  some  of  the  oxide  for  C. 

C.     Action  of  Magnesium  Oxide  with  Water. 

Place  some  of  the  oxide  from  B  on  a  piece  of  litmus 
paper  that  has  been  turned  slightly  red  with  an  acid. 
Add  a  drop  of  water  and  note  effect  on  the  litmus. 
Treat,  in  a  tt,  some  more  of  the  oxide  with  water. 
Filter  the  contents  of  the  tt.  Evaporate  the  nitrate  to 
see  if  any  considerable  amount  of  magnesium  oxide  dis- 
solved or  formed  a  soluble  compound.  In  filtering,  the 
liquid  which  filters  through  is  called  the  nitrate,  while 
the  substance  left  on  the  paper  is  called  the  precipitate. 

D.     Reaction  of  Magnesium  and   Sulphuric  Acid. 

Note.  When  two  substances  mutually  act,  i.e.,  act 
each  on  the  other,  a  reaction  is  said  to  take  place. 
Follow  through  the  chemical  change  that  takes  place 
when  magnesium  and  sulphuric  acid  are  allowed  to 
react  with  each  other.  What  do  you  mean  by  reaction 


44  CALCIUM. 

chemically?  Describe  this  experiment  in  full.  Make 
use  of  your  notes  on  all  work  with  zinc  and  with  sul- 
phuric acid.  What  do  you  call  the  substances  that  are 
the  products  in  this  case  ?  What  would  have  been  the 
products  if  you  had  taken  oxide  of  magnesium  instead 
of  magnesium  ?  Draw  diagrams  to  show  the  changes. 
Note  the  tendency  of  magnesium,  a  metal,  to  push 
the  hydrogen  from  the  acid,  and  to  take  the  place  of 
the  hydrogen  it  has  driven  out.  Mention  all  other 
cases  you  have  dealt  with  in  which  a  metal  has  pushed 
the  hydrogen  from  an  acid.  Mention  two  cases  of  this 
kind  in  which  the  metal,  when  it  began  to  act  with  the 
acid,  was  itself  already  joined  to  another  substance. 
Watch  for  the  manifestation  of  this  power  of  a  metal 
in  all  your  following  work,  and  whenever  you  note  it 
make  a  record  of  it  in  your  note-book. 


Experiment  26. 

Calcium. 
A.    The  Properties  of  Calcium. 

Examine  a  small  bit  of  this  interesting  simple  sub- 
stance, and  note  its  chief  properties,  as  color,  lustre,, 
hardness,  and  ease  with  which  the  air  acts  upon  it. 

/•'.     Oxidation  of  Calcium. 

Burn  a  small  bit  of  calcium  in  a  clean  porcelain 
crucible  and  identify  the  oxide  as  the  same  substance 
as  quick  lime.  Get  the  chief  properties  of  oxide  of 
calcium. 


HYDROXIDE   OF   CALCIUM.  45 

C.     Reaction  of  Oxide  of  Calcium  and  Water. 

Take  a  lump  of  quick  lime  weighing  about  20g. 
Put  it  in  a  porcelain  evaporating  dish.  Blow  on  it, 
from  the  wash-bottle,  water  as  long  as  the  water  is 
absorbed.  Do  not  add  any  more  water  than  this. 
Wait  a  few  minutes  for  the  change  to  take  place. 
Note  phenomena.  Remember  that  several  times  we 
have  made  acids  from  oxides  and  water.  With  moist 
litmus  paper,  both  blue  and  red,  test  the  properties 
of  the  new  substance  here  formed.  Also  test  with 
turmeric l  paper.  Test  the  solubility  of  the  new  sub- 
stance by  shaking  some  in  a  tt  with  water,  filter- 
ing, and  evaporating  the  nitrate.  Compare  with  the 
solubility  of  the  similar  compound  made  from  oxide 
of  magnesium  and  water.  Let  us  call  this  new  com- 
pound hydroxide  of  calcium  or  hydrate  of  calcium. 
Save  about  10g  of  it  for  E.  What  simple  substances 
are  in  hydroxide  of  calcium?  What  is  slaked  lime? 

D.     Action  of  Calcium  on  Water. 

Have  ready  a  short  narrow  tt,  say,  two  or  three 
inches  long  and  half  an  inch  wide.  Fit  this  tt  with 
a  one-hole  rubber  stopper  and  delivery  tube.  The 
delivery  tube  should  be  bent  like  an  S,  and  its  total 
length  should  not  be  more  than  4  or  5  inches.  Also 
have  ready,  instead  of  the  pneumatic  trough,  a  beaker 
nearly  full  of  water.  Let  there  be  standing  in  the 
beaker  an  ordinary  tt,  inverted,  and  full  of  water. 
Fill  the  short  tt  to  its  stopper  with  water,  and  put  a 
1  See  Appendix  C. 


46  SULPHATE   OF   CALCIUM. 

small  bit  of  calcium  in  this  water.  At  once  insert 
the  stopper  and  hang  the  apparatus,  by  means  of  the 
S  tube,  over  the  edge  of  the  beaker  so  that  the  gas 
evolved  shall  go  up  and  displace  the  water  in  the 
long  tt.  With  a  flaming  match  test  the  gas  evolved. 
What  is  it  ?  Whence  came  it  ?  Evaporate  the  residue 
in  the  short  tt  and  note  that  hydroxide  of  calcium  has 
been  formed.  Explain  its  formation. 

E.     Reaction  of  Hydrate  of  Calcium  and  Sulphuric  Acid. 

What  is  another  name  for  hydrate  of  calcium  ?  Take 
about  10g  of  powdered  hydrate  of  calcium.  Add  about 
30CC  of  water.  Stir  till  the  hydrate  of  calcium  is  well 
mixed  with  the  water.  Note  consistency.  Caution! 
Protect  the  eyes  from  spattering,  and  add  slowly,  with 
constant  stirring,  about  5CC  of  sulphuric  acid.  Stir  for 
about  two  minutes.  The  sulphate  of  calcium  forms 
at  once,  and  "  sets  up  "  pasty  or  even  hard.  Compare 
its  solubility  with  that  of  the  sulphates  of  iron,  zinc, 
and  magnesium.  Draw  a  diagram  to  show  the  change. 

Sulphate  of  calcium  occurs  in  nature  both  with  and 
without  water  of  crystallization.  Gypsum  is  the  kind 
that  has  the  water.  If  gypsum  be  heated  [110°-120°  C.] 
the  water  passes  off.  The  residue  is  called  plaster  of 
Paris.  Put  a  bit  of  gypsum  in  a  bulb-tube  and  heat. 
Record  observation.  Plaster  of  Paris  has  the  power 
of  again  taking  up  water,  and  in  so  doing  solidifies. 
Make  a  paste  of  plaster  of  Paris  and  water  and  watch 
it  solidify.1  Record  observations. 

1  A  cast  may  be  made  by  pressing  into  the  soft  plaster  a  coin  whose 
surface  has  been  slightly  greased  and  allowing  the  coin  to  remain  till 
the  plaster  has  "set." 


CARBONATE   OF   CALCIUM.  47 


F.     Reaction  of  Hydrate  of  Calcium  and  Carbonic  Acid. 

Note.  Recall  the  reactions  of  sulphuric  acid  and  the 
various  substances  you  have  tried  with  that  acid. 

Here  use  an  aqueous  solution  of  hydrate  of  calcium, 
called  lime-water,  best  made  as  follows.  Take  finely 
powdered  hydrate  of  calcium  and  mix  with  cold  water. 
Let  settle  for  a  few  minutes.  Pour  off,  and  reject  as 
much  of  the  liquid  as  possible,  as  it  contains  a  con- 
siderable amount  of  alkaline  impurities  dissolved  by 
the  water  from  the  lime.  Mix  this  washed  hydrate  of 
calcium  with  more  cold  water.  Filter.  Keep  the 
nitrate  in  a  well-corked  bottle.  Take  about  10CC  of 
the  hydrate  of  calcium  solution  and  20CC  of  carbonic 
acid  water.1  Mix,  and  heat  in  a  beaker  until  the  new 
substance  appears.  Let  settle,  and  decant,  or  filter. 
Decant  means  to  pour  off  carefully,  without  filtering, 
a  clear  liquid  from  a  precipitate  that  has  settled  from 
the  liquid.  Examine  the  new  substance  and  recognize 
it  as  the  same  substance  as  powdered  marble  or  chalk. 
Let  us  call  it  carbonate  of  calcium.  Test  its  solubility 
in  water.  Why  did  it  not  appear  [when  the  carbonic 
acid  and  hydrate  of  calcium  were  mixed]  until  you 
heated  ?  In  order  to  answer  the  last  question  proceed 
as  follows.  Put  about  10CC  of  lime-water  in  a  tt.  Add 

1  The  instructor  should  prepare  the  carbonic  acid  water  by  passing 
carbon  dioxide  gas  into  a  bottle  half  filled  with  cold  water,  and  shak- 
ing till  the  water  has  absorbed  all  the  gas  it  can,  or,  better,  buy  the 
water  [soda  water]  from  any  soda-fountain  keeper.  Keep  the  carbonic 
acid  water  in  a  tightly-stoppered  bottle  in  a  cool  place.  A  beer  bottle 
with  a  rubber  stopper  that  can  be  snapped  down  is  good  for  keeping 
this  water. 


48  HARD   WATER. 

lcc,  only,  of  carbonic  acid  water.  Note  result,  then  add 
the  other  19CC  of  carbonic  acid  water  and  shake  to  mix. 
•Water  which  has  dissolved  sulphate  of  calcium  is  called 
permanently  hard  water.  Water  [containing  carbonic 
acid,  e.g.,  water  which  has  made  its  way  through  swamps 
where  there  is  decomposing  vegetable  matter],  which 
has  dissolved  carbonate  of  calcium  is  called  temporarily 
hard  water.  Why  is  one  called  permanently  hard  and 
the  other  temporarily?  How  may  temporarily  hard 
water  be  made  soft?  Hard  water  is  said  to  "kill" 
soap.  Prepare  a  solution  of  soap  thus.  Put  about 
one  gram  of  shavings  from  soap  in  about  10CC  of  water 
in  a  tt.  Shake  till  most  of  the  soap  has  dissolved. 
Have  ready  two  tts,  in  one  of  which  are  10CC  of 
distilled  water,  and  in  the  other  an  equal  volume  of 
hard  water,  e.g.,  water  that  has  been  filtered  from 
sulphate  of  calcium,  or  water  that,  by  means  of  car- 
bonic acid,  has  been  made  to  take  up  carbonate  of 
calcium.  By  means  of  a  pipette,  or  long  tube  drawn 
out  at  the  end  to  a  wash-bottle  tip,  take  up  some  of 
the  clear  soap  solution  and  drop  this,  drop  by  drop, 
alternately  in  the  tt  of  pure  water  and  in  the  tt  of 
hard  water.  Shake  each  tt  after  every  two  drops, 
and  note  in  which  tt  frothing  is  produced  the  sooner. 
Note  how  many  drops  are  required  to  produce  frothing 
in  each  case.  What  inference  do  you  draw  in  regard  to 
the  relative  values  of  pure  and  hard  waters  for  washing 
purposes?  Define  stalactite.  Define  stalagmite. 

When  oxide  of  zinc  acted  with  sulphuric  acid,  and 
sulphate  of  zinc  was  formed,  we  concluded  that  the 
reason  no  hydrogen  was  given  off  [as  there  was  when 


LIME   WATEK.  49 

zinc  and  sulphuric  acid  were  put  together]  was  because 
the  hydrogen  joined  the  oxygen  of  the  zinc  oxide  and 
formed  water.  Remember  that  hydrate  of  calcium  is 
made  of  oxide  of  calcium  and  water.  If  a  similar 
thing  happens  when  sulphate  of  calcium  is  formed, 
what  simple  things  must  there  be  in  sulphate  of  cal- 
cium? And  if  a  similar  thing  happens  when  hydrate 
of  calcium  and  carbonic  acid  react  to  form  the  carbonate 
of  calcium,  what  simple  things  must  there  be  in  car- 
bonate of  calcium?  As  confirmation  of  your  answer 
to  the  last  question,  pass  the  non-combustible  oxide  of 
carbon  through  a  tt  of  hydrate  of  calcium  in  aqueous 
solution  [lime-water],  and  note  that  the  same  carbonate 
of  calcium  is  formed.  Explain  the  formation,  making 
use  of  a  diagram. 

Note.  Lime-water  is  a  good  test  for  the  presence  of 
the  non-combustible  oxide  of  carbon  because  the  two  so 
readily  react  and  form  carbonate  of  calcium. 

[1]  Hold  a  tt  inverted  over  the  flame  of  a  candle. 
Then  add  about  2CC  of  lime-water.  Shake,  and  note 
effect. 

[2]  Try  the  products  of  combustion  from  the  flame 
of  common  house  gas  with  lime-water.  Also  test  the 
gas  itself  for  oxide  of  carbon. 

[3]  Take  a  tt  half  full  of  lime-water  and,  by  means 
of  a  glass  tube  reaching  well  into  the  lime-water,  blow 
your  breath  several  times  through  the  liquid.  Note 
effect,  and  explain.  The  non-combustible  oxide  of  car- 
bon, or  carbon  dioxide,  is  also  called  carbonic  anhydride. 
What  is  the  meaning  of  the  term  anhydride?  Why 
applied  to  this  oxide? 


50  ANALYSIS    OF    MARBLE. 

G.     Analysis  of  Marble  [calcic  carbonate]. 

Note.  We  have  already  made  a  synthesis  of  marble. 
What  is  a  synthesis  ?  Mention  several  syntheses  you 
have  made.  Explain  in  full  the  synthesis  of  marble. 

Take  a  piece  of  large  hard  glass  combustion  tube 
about  15cm  long  and  closed  at  one  end.  [Best  get  a 
piece  of  tube  about  30cm  long  and  make  two  15cm 
tubes  by  melting  and  pulling  apart  in  the  middle.] 
Be  sure  the  end  is  good  and  stout,  not  cooled  too 
quickly,  and  not  ending  in  a  lump  of  thick  glass  that 
is  likely  to  crack  off  when  the  tube  is  again  heated. 
Fit  a  cork  and  delivery  tube  to  the  open  end.  Put 
in  the  tube  about  10g  of  coarsely  powdered  marble. 
Caution !  Let  the  delivery  tube  dip  only  the  least 
possible  distance  below  the  surface  of  the  pneumatic 
trough,  as  deep  dipping  causes  back  pressure  which  is 
apt  to  blow  out  the  softened  glass.  Heat  the  marble 
with  a  blast>-lamp.  Apply  the  blast  gently  at  first. 
Collect  in  tts  the  gas  evolved.  Test  it.  What  is 
it?  Prove  that  your  inference  is  correct.  [See  note 
at  end  of  I1.]  State  how  you  have  already  proved  of 
what  this  constituent  of  marble  is  composed.  As  it 
is  impossible  to  make  all  the  gas  come  off  in  a  closed 
tube,  i.e.,  without  a  current  to  carry  it  away,  take  a 
small  lump  of  marble,  hold  it  with  forceps,  and  heat 
in  the  blast-lamp  flame  till  it  glows  brightly.  Note 
the  lime  [or  calcium]  light.  Examine  the  residue,  and 
recognize  it  as  quick  lime,  i.e.,  oxide  of  calcium.  How 
did  you  form  oxide  of  calcium  ?  [See  B.} 

Mix  well  one  gram  of  powdered  oxide  of  calcium 
with  half  a  gram  of  powdered  magnesium.  Put  the 


MARBLE   AND    ACID.  51 

mixture  in  a  small  dipper.  Caution!  Keep  the  eyes 
away.  Heat  over  a  Bunsen  burner  flame.  The  mag- 
nesium takes  the  oxygen  away  from  the  calcium  with 
great  eagerness.  Note  phenomena.  Have  ready  the 
short  tt  and  fittings  used  in  D.  Put  the  contents  of 
the  dipper  in  the  tt.  Nearly  fill  the  tt  with  water. 
Put  in  the  stopper  quickly.  Catch  the  gas  given  off. 
What  is  it  ?  Use  the  flame  test.  What  does  the  evolu- 
tion of  this  gas  prove  in  regard  to  the  chemical  change? 
What  happened  to  the  magnesium?  Arrange  your 
analysis  in  the  form  of  a  table.  What  is  an  analysis  ? 

H.     Reaction  of  Marble  and  Sulphuric  Acid. 

State  the  simple  substances  that  make  marble.  State 
the  simple  substances  that  make  sulphuric  acid.  Take 
10g  of  powdered  marble.  Put  them  in  a  flask,  add  30CC 
of  water  and  then  6CC  of  sulphuric  acid.  Catch  the  gas 
evolved,  and  test  it.  What  is  it  ?  How  do  you  prove 
your  answer  correct  ? 

Note  how  the  new  white  substance  formed  collects 
around  the  marble,  prevents  the  acid  from  coming  in 
contact  with  the  marble,  and  thus  hinders  the  action. 
If  the  new  white  substance  was  readily  soluble  in  the 
water,  there  would  be  no  such  hindrance.  Many  sub- 
stances which  are  soluble  in  water  are  not  soluble  in 
sulphuric  acid,  he»ce  in  many  cases,  e.g.,  in  the  prep- 
aration of  hydrogen  by  means  of  zinc  and  sulphuric 
acid,  and  in  the  preparation  of  sulphide  of  hydrogen 
from  sulphide  of  iron  and  sulphuric  acid,  it  is  necessary 
to  use  water  to  dissolve  some  product  which  otherwise 
would  retard,  if  not  actually  prevent,  the  action. 


52  SODIUM. 

Evaporate  the  residue  from  the  flask  and  recognize 
it  as  sulphate  of  calcium.  If  there  are  bad  fumes  on 
evaporating,  put  the  residue  under  the  hood,1  and  evap- 
orate there.  Prove  that  the  residue  is  not  carbonate 
of  calcium.  How  do  you  prove  this?  Explain  the 
chemical  change  that  has  taken  place.  How  can  you 
detect  a  carbonate  ? 


Experiment  27. 

Sodium.     [Latin  name,  Natrium.] 
A.     The  Properties  of  Sodium. 

Examine  a  small  bit  of  sodium,2  and  get  the  chief 
properties,  particularly  color,  lustre,  hardness,  and 
attraction  for  oxygen.  Caution!  The  attraction  of 
sodium  for  oxygen  makes  sodium  a  dangerous  sub- 
stance to  handle.  When  experimenting  with  sodium 
keep  it  away  from  every  substance  that  has  oxygen, 
e.g.,  water,  and  the  moisture  of  your  hand,  even. 

B.     Oxidation  of  Sodium. 

Let  a  bit  of  freshly  cut  sodium  be  exposed  to  the 
air  for  five  seconds.  What  happens?  What  is  the 
coating  formed?  Place  a  bit  of  sodium  in  a  porce- 
lain crucible  and,  protecting  the  eyes  by  a  glass  plate, 
warm.  Note  phenomenon.  Save  some  of  the  result- 
ing substance  for  C. 

1  See  Appendix  G. 

2  Sodium  is  a  dangerous  substance  if  handled  carelessly,  or  allowed 
to  get  into  water.     It  should  be  kept  under  kerosene,  or  some  similar 
liquid,  whenever  not  in  use, 


SODIUM   WITH   WATER.  53 

C.    Reaction  of  Oxide  of  Sodium  and  Water. 

Treat  the  oxide  of  sodium  made  in  B  with  a  few 
drops  of  water.  Protect  the  eyes  as  in  B.  Test  the 
solution  with  test  papers.  Is  it  acid  or  the  opposite? 
Compare  with  the  action  of  other  oxides  and  water. 
Filter,  —  if  dirty,  —  and  evaporate  to  dryness.  Examine 
the  new  substance,  and  let  us  call  it  hydrate  [or  better, 
hydroxide]  of  sodium.  Why  call  it  hydroxide  ?  Why 
hydrate  ?  Rub  a  little  sodium  hydroxide  between  the 
fingers  and  note  the  greasy  feeling.  Put  a  little 
hydroxide  of  sodium  on  the  bottom  of  a  beaker  and 
leave  it  exposed  to  the  air  for  an  hour.  The  peculiar 
property  thus  manifested  is  called  deliquescence. 
What  is  deliquescence? 

Note.  Substances  that  have  the  opposite  effect  from 
acids  on  test  papers  are  said  to  be  alkaline. 

D.     Action  of  Sodium  on  Water. 

Have  ready,  in  a  beaker,  about  100CC  of  cold  water 
and  a  tt,  upside  down,  filled  with  water.  Make  a  little 
wire  gauze  net  on  the  end  of  a  wire.  Wrap  a  bit  of 
sodium,  not  larger  than  a  small  pea,  in  the  gauze  and 
plunge  it  below  the  water.  Catch,  in  the  invested  tt, 
the  gas  evolved.  Caution!  Keep  the  eyes  well  pro- 
tected, for  if  the  sodium  gets  out  of  the  gauze  an 
explosion  is  likely  to  follow.  Why?  Examine  the 
gas  caught.  What  is  it?  Filter  the  liquid  left  in 
the  beaker,  if  any  impurities  from  the  gauze  have  got 
in.  Evaporate  to  dryness  in  a  porcelain  dish.  Test 
a  bit  of  the  substance  with  moist  test  papers,  and  by 
feeling.  What  is  it  ?  Explain  its  formation. 


54  NEUTRALIZATION. 

E.     Reaction  of  Sodium  Hydroxide  and  Sulphuric  Acid. 

Make  two  aqueous  solutions  as  follows  :  [1]  Take 
100CC  of  water  and  5CC  of  sulphuric  acid.  [2]  Take 
100CC  of  water  and  8g  of  hydroxide  of  sodium.  Have 
ready  a  porcelain  evaporating  dish.  Fill  about  one 
fourth  of  the  dish  with  the  sulphuric  acid  solution,  and 
add  about  as  much  hydroxide  solution.  Stir.  Then 
add  first  one  and  then  the  other  till  drops  taken  out 
on  a  rod  and  touched  to  test  papers  show  the  contents 
of  the  dish  to  be  neutral,  i.e.,  neither  acid  nor  alkaline. 
Note,  this  process  is  called  neutralization.  Evaporate 
the  liquid  in  the  dish  to  crystallization.  Examine  the 
crystals,  and  get  their  properties.  What  are  they? 
Compare  Ex.  26,  JE.  Compare  also  the  formation  of 
the  products  in  Exs.  21,  22,  23,  0,  and  25,  D.  Explain 
the  formation  of  the  compound  in  this  case.  What 
simple  things  in  this  compound?  Is  any  water  of 
crystallization  present?  Test  the  answer  to  the  last 
question  by  experiment. 

F.     Reaction  of  Sodium  Hydroxide  and  Carbonic  Acid. 

Make  an  aqueous  solution  of  sodium  hydrate  of  the 
proportions  lg  hydrate  and  20CC  water.  Take  about 
10CC  of  carbonic  acid  solution,  and  add  the  solution  of 
hydroxide  of  sodium  till  the  liquid  is  no  longer  acid. 
Evaporate  to  dryness.  Examine  the  residue.  What 
is  it?  It  is  composed  of  what  simple  substances? 
What  is  sal  soda?  Test  sal  soda  for  a  carbonate. 
Leave  a  good  clear  crystal  of  sal  soda  exposed  to  the 
air  for  an  hour  or  more.  Note  the  phenomenon.  The 
property  that  here  manifests  itself  is  called  efflores- 


SODIUM    AMALGAM.  55 

cence.      What  is  efflorescence?      Compare  with  deli- 
quescence. 

G.     Reaction  of  Hydrate  of  Sodium  and  the  Non- 
Combustible  Oxide  of  Carbon. 

Take  0.5s  of  hydrate  of  sodium.  Dissolve  it  in  a  tt 
half  full  of  water.  Pass  the  dioxide  of  carbon  through 
the  liquid  for  about  two  minutes.  Evaporate  to  dryness. 
Examine  the  residue.  Dissolve  the  residue  in  5CC  of 
water,  and  test  for  a  carbonate.  Explain  the  formation 
of  a  carbonate  in  this  case. 

H.     Reaction  of  Carbonate  of  Sodium  and  Sulphuric  Acid. 

Parallel  to  E.  State  factors  and  products.  Give 
results  in  full,  explaining,  particularly,  the  chemical 
change. 

I.     Reaction  of  Sodium  and  Mercury. 
Caution !          Caution !          Caution ! 

Use  extreme  care  and  do  not  let  particles  fly  in  your 
eyes  when  the  two  substances  join. 

Take  a  bit  of  sodium  and  a  globule  of  mercury. 
Support  the  cover  to  a  porcelain  crucible  on  a  ring 
of  the  ring  stand.  Warm  the  cover.  Pour  on  a 
globule  of  mercury  about  2mm  in  diameter.  Then  put 
a  bit  of  sodium  of  about  the  same  size  near  the  mer- 
cury. Set  the  stand  on  the  floor.  Stand  at  a  distance, 
and  poke,  with  a  long  rod,  the  sodium  into  the  mercury. 
Note  phenomena.  Examine  the  resulting  product.  A 
substance  formed  from  mercury  and  another  metal  is 
called  an  amalgam.  This  then  is  sodium  amalgam. 


56  CHLOUItfE. 

Throw  the  amalgam  into  a  small  dish  of  water.  Note 
that  the  sodium  acts  as  pure  sodium,  but  less  rapidly, 
and  that  [after  a  few  hours],  when  the  sodium  is  all 
gone  [into  what?],  the  original  mercury  remains.  Give 
chief  properties  of  sodium  amalgam. 

Review  your  work  with  sodium  and  its  compounds, 
and  make  diagrams  to  express  the  chemical  changes 
that  you  have  brought  about. 


Experiment  28. 
Chlorine. 

Take  a  jar  of  chlorine.1  Get  the  chief  properties  of 
chlorine,  particularly  its  color  and  odor.  Also  note  its 
action  on  moist  litmus.  Caution!  Chlorine  is  very 
irritating  to  the  mucous  membranes.  In  getting  the 
odor,  breathe  only  the  least  possible  amount.  In  large 
quantities  chlorine  is  a  violent  poison. 


Experiment  29. 

Chlorides. 

A.    Chloride  of  Hydrogen. 
Caution !          Caution !          Caution ! 

Chlorine  and  hydrogen  unite  with  frightful  violence. 
Always  think  what  you  are  going  to  do  with  chlorine 
before  you  act.  Never  let  hydrogen  and  chlorine  mix 

1  Chlorine  gas  should  be  provided  by  the  instructor  and  given,  in  tts 
and  fruit  jars,  to  the  students  as  needed.  For  a  method  for  preparing 
chlorine,  see  Appendix  H. 


CHLOKIDE   OF   SODIUM.  57 

accidentally.  Never  let  a  mixture  of  chlorine  and 
hydrogen  remain  standing  in  the  light  or  near  a  fire. 
A  mixture  of  chlorine  and  hydrogen  explodes  sponta- 
neously if  left  in  the  sunlight.  Finally,  —  use  your 
utmost  good  judgment. 

Have  ready  a  jar  of  chlorine  gas  and  a  flask  that  is 
delivering  hydrogen  gas  through  a  rubber  tube  ending 
with  a  "hard  glass  wash-bottle  tip.  When  safe,  light 
the  stream  of  hydrogen  gas,  carefully  raise  the  cover  a 
little  from  the  jar  of  chlorine,  and  slowly  pass  the  hydro- 
gen flame  down  into  the  chlorine.  Note  the  change 
in  the  flame  as  chlorine,  instead  of  oxygen,  joins  the 
hydrogen.  Note  the  properties  of  the  product  of  the 
union,  particularly  state  and  acidity.  Chloride  of 
hydrogen  is  commonly  called  hydrochloric  acid. 

B.     Chloride  of  Sodium. 

Have  ready  a  tt  of  dry  chlorine,  and  a  piece  of  freshly- 
cut  sodium.  The  piece  of  sodium  should  be  a  slice  cut 
very  thin,  and  large  enough  to  cover  about  one  quarter 
of  the  nail  of  your  little  finger.  Keep  the  tt  well  away 
from  the  eyes.  Drop  the  sodium  in  the  tt.  Cork,  and  let 
stand  over  night.  Spread  out  the  new  substance  to  air. 
Get  the  properties.  Try,  by  taste,  to  recognize  it  as 
common  table  salt.  Do  not  taste  if  any  unchanged 
sodium  remains.  Why?  What  simple  substances  form 
table  salt  ?  Let  us  call  it  chloride  of  sodium. 

C.     Preparation  of  Hydrochloric  Acid  on  a  Large  Scale. 

Take  sulphuric  acid  and  table  salt.  State  the  simple 
substances  that  make  up  each  of  these  compounds. 


58  HYDROCHLORIC   ACID. 

Have  ready  a  small  flask  with  cork  and  delivery  tube. 
Put  about  10g  of  the  chloride  of  sodium  in  the  flask. 
Add  about  15CC  of  sulphuric  acid.  Warm  if  necessary 
to  start  the  action.  Catch  the  gas  by  displacement. 
It  will  be  found  to  be  a  heavy  gas.  Why  not  here  use 
the  water  trough  for  catching  ?  Fill  at  least  three  jars. 
Be  sure  the  jars  are/^ZZ.  Tell  when  full  by  the  smell. 
What  is  this  gas?  How  have  you  made  it  before? 
Now  get  the  properties  of  this  gas.  Explain  its  for- 
mation from  table  salt  and  sulphuric  acid.  Make  a 
diagram  to  show  the  simple  substances,  and  their 
change  of  place.  Compare  the  action  of  sulphuric 
acid  in  this  case  with  its  action  on  sulphide  of  iron. 
State  the  factors  and  the  products  in  both  cases.  Save 
two  jars  of  hydrochloric  acid  gas  for  subsequent  use. 

D.     Solubility  of  Hydrochloric  Acid. 

» 
Take  a  jar  of  hydrochloric  acid  gas  [made  in  C].    Put 

in  about  20CC  of  water.  Snap  on  the  cover.  Shake. 
Open  under  water.  Is  the  gas  soluble  ?  Test,  with 
litmus,  for  the  acid  property  of  the  liquid.  For  con- 
venience in  handling,  hydrochloric  acid  is  usually  sold 
in  aqueous  solution.  The  crude  hydrochloric  acid  of 
trade  is  called  muriatic  acid.  It  is  yellow  from 
impurities. 

E.     Reaction  of  Hydrochloric  Acid  and  Marble. 

Have  ready  a  small  flask  fitted  with  a  one-hole  cork 
and  delivery  tube.  Put  a  few  lumps  of  marble  in  the 
flask,  and  cover  them  with  aqueous  hydrochloric  acid. 
Catch  the  gas  evolved  and  test  it.  What  is  it?  After 


HYDEOCHLOKIC    ACID.  59 

the  acid  has  ceased  acting,  remove  any  marble  that  may 
be  left,  and  evaporate  the  liquid  to  dry  ness.  Of  what 
is  marble  composed?  What  then  must  be  the  residue 
from  evaporation?  Note  the  chief  properties  of  chlo- 
ride of  calcium.  Leave  a  little  exposed  for  an  hour 
or  two  to  the  air  of  the  laboratory.  What  property  do 
you  note  ?  Why  is  chloride  of  calcium  a  good  chemical 
with  which  to  dry  gases  and  other  substances  ? 

Had  sal  soda  been  used  in  this  experiment  instead  of 
marble,  what  gas  would  have  been  given  off,  and  what 
would  the  residue  on  evaporation  have  been  ? 

Draw  diagrams  to  show  the  reactions,  both  when  marble 
was  used  and  in  a  case  in  which  sal  soda  is  substituted. 

Note.  This  experiment  teaches  the  best  way  to  pre- 
pare a  certain  gas  on  a  large  scale.  What  gas? 

F.     Action  of  Sodium  on  Hydrochloric  Acid. 

Have  ready  a  jar  of  hydrochloric  acid  gas  and  some 
sodium  amalgam.  To  insure  success  the  jar  must  be 
full  of  the  gas,  and  the  sodium  amalgam  must  have 
been  recently  made,  and  freshly  broken  into  very  small 
pieces.1  The  hydrochloric  acid  gas  must  have  been 
dried  by  passing  it  through  a  catch-bottle  of  sulphuric 
acid,  or  there  will  be  danger  of  an  explosion.  Why? 
Nor  must  there  be  any  moisture  in  the  jar  at  all.  Be 
sure  the  washer  to  the  jar  is  well  greased. 

Sodium  amalgam  is  here  used,  instead  of  pure  sodium, 
because  the  mercury  modifies  the  action  of  the  sodium 
and  makes  it  controllable.  That  the  mercury  itself 
does  not  act,  to  any  appreciable  extent,  on  the  acid,  may 

1  For  the  preparation,  on  the  large  scale,  of  sodium  amalgam  see 
Appendix  I. 


60  POTASSIUM. 

be  shown,   after  the  experiment,  by  noting  that  the 
mercury,  in  liquid  form,  may  be  found  in  the  trough. 

To  the  jar  of  hydrochloric  acid  gas  add  about  25* 
of  sodium  amalgam.  Shake  well.  Note  phenomenon. 
Open  under  water.  At  once  note  how  much  vacuum 
there  was,  at  the  same  time  letting  the  unused  amalgam 
drop  into  the  trough.  [A  zinc  trough  must  not  be 
used  here  because  mercury  amalgamates  with  zinc  and 
makes  it  brittle.]  Put  the  cover  on  at  once,  but  do 
not  seal,  for,  if  any  amalgam  is  left  in  the  jar,  there 
may  be  an  explosion.  Why  ?  At  once  apply  a  flame 
to  the  gas  remaining  in  the  jar.  What  gas  is  this? 
Of  what  is  hydrochloric  acid  made?  What  becomes 
of  the  chlorine  in  this  experiment? 

O.  Action  of  Sodium  Hydroxide  with  Hydrochloric  Acid. 
Dissolve  about  5g  of  sodium  hydroxide  in  about  50CC 
of  water.  Neutralize  this  solution  with  one  of  some- 
what diluted  hydrochloric  acid.  Evaporate  till  crystals 
'begin  to  form.  Examine  the  crystals  and  recognize 
them  by  their  color,  form,  and  taste  as  table  salt. 
Explain  their  formation.  What  was  the  other  product 
of  the  chemical  change  ?  Draw  a  diagram. 


Experiment  3O. 
Potassium.    [Latin  name,  Kalium.] 

Note,  as  you  work  with  potassium,  how  closely  it 
resembles  sodium,  and  how  much  like  sodium  com- 
pounds are  the  corresponding  potassium  compounds. 
Caution !  Same  as  in  the  use  of  sodium. 


POTASSIUM   COMPOUNDS.  61 

A.     The  Properties  of  Potassium. 

Examine  a  small  bit  of  potassium  and  get  its  chief 
properties ;  particularly,  color,  lustre,  hardness,  and 
affinity  for  oxygen.  Note  that  it  has  metallic  prop- 
erties. Is  it  a  metal? 

11     Oxidation  of  Potassium. 

Take  a  bit  of  potassium  and  place  it  on  a  crucible 
cover  exposed  to  the  air.  Cut  the  potassium  to  expose 
more  surface  to  the  oxygen  of  the  air.  Note  the 
rapidity  of  the  oxidation. 

C.     Reaction  of  Oxide  of  Potassium  and  Water. 
Parallel  to  Ex.  27,  O. 

D.    Reaction  of  Potassium  and  Water. 

Have  ready  a  fruit  jar  with  enough  water  in  it  to 
cover  the  bottom.  Drop  in  a  bit  of  potassium  as 
large  as  a  small  pea.  Instantly  step  back  two  yards 
or  more.  Note  phenomena.  Explain  the  action  com- 
pletely. Evaporate  the  liquid  to  dryness.  Test  a 
bit  of  the  residue  with  moist  test  papers  and  by  feeling. 
What  is  it?  Explain  its  formation. 

E.     Action  of  Potassium  on  the  Dioxide  of  Carbon. 

Have  ready  a  piece  of  hard  glass  tube  about  10  inches 
long.  Also  a  generator  which  is  delivering  dry  car- 
bonic dioxide.  [See  note  at  end  of  Experiment  29,  E.'] 
Put  in  the  tube  a  piece  of  potassium  as  large  as  a  small 
pea.  Attach  the  tube  to  the  generator,  and  clamp 


62  POTASSIUM   COMPOUNDS. 

it  at  a  convenient  height  for  heating  with  a  Bunsen 
burner.  Pass  the  oxide  of  carbon  until  it  will  put  out 
a  match  at  the  open  end  of  the  tube.  Then  warm  the 
potassium.  Note  that  it  burns  at  the  expense  of  the 
oxygen  of  the  carbonic  dioxide.  Note  the  black  particles 
of  carbon  that  have  lost  their  oxygen:  note  also  the 
white  powder.  What  is  the  latter?  Answer  this  as 
follows:  After  the  action  has  ceased  and  the  tube  is 
cool,  wash  out  the  tube  into  a  beaker,  using  as  little 
water  as  possible.  Filter  from  the  carbon.  Test  the 
nitrate  for  a  carbonate.  How  test?  Explain  com- 
pletely the  formation  of  a  carbonate. 

F.     Reaction  of  Potassium  Hydroxide  and  Sulphuric  Acid. 

Parallel  to  Ex.  27,  E.  Examine  the  sulphate  of 
potassium  carefully,  as  you  will  be  referred  to  this 
again.  Note  particularly  the  color,  form,  and  taste 
of  the  crystals.  Hold  some  in  a  Bunsen  flame  and 
note  flame  coloration.  Heat  some  of  the  crystals  in 
a  porcelain  dish  and  note  that  no  water  of  crystalliza- 
tion is  present.  Be  sure  you  can  recognize  this  substance 
again. 

Draw  a  diagram  to  show  the  chemical  reaction. 
Also  note  the  invariable  tendency,  again  manifested 
in  this  change,  of  a  metal  to  push  the  hydrogen  from 
an  acid.  Mention  all  the  other  cases  you  can  recall 
in  which  this  tendency  has  been  manifested. 

Test  the  flame  coloration  of  all  the  potassium  com- 
pounds you  can  find.  Note  the  flame  coloration  pro- 
duced by  table  salt.  Test  the  flame  coloration  of  all 
the  sodium  compounds  you  can  find. 


NITROGEN.  63 

Experiment  31. 
Nitrogen. 

We  early  learned  that  about  one  fifth  the  volume  of 
the  air  is  oxygen.  Let  us  now  examine  the  other 
constituent.  Have  ready  a  large  cork  with  a  little 
hollow  dug  out  of  its  smaller  end.  Put  about  0.3g 
of  phosphorus  in  the  hollow  of  the  cork.  Float  the 
cork  on  water  in  the  pneumatic  trough.  Set  fire  to 
the  phosphorus,  and  invert  a  jar  of  air  over  the  burning 
phosphorus.  What  becomes  of  the  oxygen  of  the  air? 
What  becomes  of  the  oxide  of  phosphorus  ?  Examine 
the  remaining  gas.  Compare  it  with  all  the  gases  you 
have  made.  Let  us  call  it  nitrogen.  Give  the  prop- 
erties of  nitrogen. 


Experiment  32. 

A  Chemical  Investigation. 

There  is  often  found  as  an  efflorescence  from  the  soil 
in  hot  countries,  especially  in  Bengal,  Egypt,  Persia, 
and  a  few  places  in  America,  a  white  substance  of  a 
salt-like  nature  called  nitre  or  saltpeter.  This  sub- 
stance is  used  largely  for  making  gunpowder,  and  often 
for  making  one  of  the  most  powerful  acids  known,  — 
nitric  acid.  Let  us  direct  an  investigation  to  finding 
what  simple  substances  are  in  nitre,  and  what  ones  are 
in  nitric  acid  which  is  made  from  nitre.  First  let  us 
prepare  nitric  acid. 


64  A   CHEMICAL   INVESTIGATION. 

A.     Preparation  of  Nitric  Acid. 

Take  nitre  and  sulphuric  acid.  Put  in  a  small, 
tubulated,  glass-stoppered  glass  retort,  30g  of  nitre 
and  10CC  of  sulphuric  acid.  Heat,  gently  at  first, 
using  a  tripod  and  gauze.  Caution !  Do  not  put 
the  hand  where  the  molten  mass  or  the  acid  could  harm 
it,  should  there  be  an  accident.  Distil  10  or  15CC  of 
liquid,  letting  it  drop  so  slowly  that  little  or  none 
of  the  vapor  fails  to  condense.  Get  the  properties  of 
the  liquid.  It  is  so  powerful  that  before  testing  it 
with  test  papers  for  acid  properties,  some  of  it  should 
be  diluted  with  several  times  its  volume  of  water  or 
it  will  destroy  the  paper  itself.  Let  us  call  the  liquid 
nitric  acid.  Have  ready  about  100CC  of  water  heated 
to  80°  or  90°  C.  When  the  liquid  in  the  retort  has 
cooled  somewhat,  insert  a  funnel  in  the  tubulature  of 
the  retort,  and  cautiously  pour  the  hot  water  directly 
into  the  midst  of  the  liquid.  Caution!  If  the  con- 
tents of  the  retort  are  too  hot,  there  is  danger  that  the 
hot  water  will  be  converted  into  steam  so  rapidly  that 
an  explosion  may  result,  and  if  too  cold,  crystals  may 
fix  themselves  so  firmly  to  the  sides  of  the  retort  that 
they  cannot  be  removed  without  danger  of  breaking 
the  glass.  When  the  water  is  all  added,  stir  the  con- 
tents of  the  retort  till  the  crystals  are  either  dissolved 
or  broken  enough  to  be  removed.  Fill  an  evaporating 
dish  with  the  liquid  from  the  retort.  Evaporate  to 
crystallization.  Examine  the  crystals.  Test  the  flame 
coloration  produced  by  these  crystals  and  satisfy  your- 
self by  color,  taste,  form,  etc.,  that  you  now  have  the 
same  substance  made  in  Ex,  30,  F.  [It  may  be  neces- 


A    CHEMICAL    INVESTIGATION.  65 

sary,  before  you  can  get  good  crystals,  to  wash  out  the 
sulphuric  and  nitric  acids  that  remain.  Do  this  wash- 
ing by  putting  the  crystals  oh  a  filter,  in  a  funnel,  and 
letting  a  very  small  amount  of  cold  water  run  through. 
Why  not  let  much  water  run  through?  It  would  be 
well  to  recrystallize  the  substance  from  hot  water  to 
purify  it.]  What  is  the  substance  in  hand  ?  Of  what 
simple  substances  is  it  formed?  Remembering  the 
effect  of  metals  on  the  hydrogen  of  acids,  what  do  you 
say  here  came  from  the  sulphuric  acid?  What  from  the 
nitre  ?  What  then  did  the  sulphuric  acid  lose,  and  what 
became  of  this  that  left  the  sulphuric  acid?  Review 
all  the  acids  that  you  have  made,  i.e.,  sulphurous, 
sulphuric,  phosphoric,  carbonic,  hydrochloric,  and  note 
that  all  have  hydrogen  in  them.  What,  then,  do  you 
say  is  one  simple  substance  in  nitre?  What  is  one 
simple  substance  in  nitric  acid?  As  confirmation  of 
your  belief  that  there  is  hydrogen  in  nitric  acid  allow 
magnesium  to  act  on  some  of  the  acid,  as  follows. 

B.     Action  of  Magnesium  on  Nitric  Acid. 

Have  ready  a  tt  fitted  with  a  one-hole  cork  and 
delivery  tube  reaching  to  a  pneumatic  water  trough. 
Put  about  5CC  of  nitric  acid  in  the  tt,  and  add  about 
10CC  of  water.  Put  in  a  small  strip  of  magnesium 
ribbon,  and  at  once  insert  the  cork  and  catch  the 
gas  in  a  tt  at  the  trough.  Apply  a  flame.  What 
gas  is  present? 

C.     Action  of  Copper  on  Nitric  Acid. 

Take  copper  and  nitric  acid.  Put  about  50g  of 
copper  clippings  in  a  small  flask.  The  flask  should 


66  CHEMICAL    INVESTIGATION. 

have  a  two-hole  cork  through  which  passes  a  funnel 
tube  as  well  as  a  delivery  tube.  Add  enough  water 
to  seal  the  funnel  tube.  Then  add  a  mixture  of  1  vol. 
of  nitric  acid  to  1  vol.  of  water.  Add  this  mixture 
a  little  at  a  time.  Collect  the  gas  over  water.  Catch 
three  jars  of  it.  Reject  the  first.  Why?  Get  the 
properties  of  the  gas  from  the  second.  Is  it  hydrogen  ? 
Note  that  on  exposure  to  the  air  it  oxidizes  spontane- 
ously, and  the  oxide  formed  is  brown.  In  the  third 
jar  of  gas  burn  about  0.3g  of  phosphorus.  Have  the 
phosphorus  well  on  fire  before  plunging  into  the  jar. 
Take  all  the  usual  precautions.  Note  the  formation  of 
the  white  oxide  of  phosphorus.  Therefore  the  sub- 
stance under  examination  had  oxygen  in  it.  How 
much  oxygen  ?  Answer  this  by  opening  under  water. 
From  what  sources  may  the  oxygen  have  come  ?  Test 
the  residual  gas.  Use  the  flame  test.  Is  it  carbonic 
dioxide  or  nitrogen?  Whence  came  this  gas?  What 
simple  substances  have  we  now  proved  to  be  in  nitric 
acid? 

D.     Action  of  Carbon  on  Nitric  Acid. 

Take  nitric  acid  and  charcoal.  Put  in  a  Kjeldahl 
flask  about  50CC  of  nitric  acid.  Add  three  or  four 
sticks  of  charcoal,  each  about  as  large  as  your  little 
finger.  Have  a  delivery  tube  leading  to  a  catch-bottle 
containing  water  to  catch  any  nitric  acid  that  may  pass 
over.  Why  must  the  acid  be  caught?  Answer  this 
question  after  the  experiment  is  finished.  Warm  the 
nitric  acid  till  gas  passes  off  freely.  After  the  gas  has 
passed  long  enough  to  remove  all  air  from  the  flask, 
catch-bottle,  and  tubes,  collect  some  in  Us  and  examine 


A   CHEMICAL   INVESTIGATION.  67 

it.  What  is  it?  Pass  some  into  a  tt  containing  an 
aqueous  solution  of  calcic  hydroxide.  What  happens  ? 
Explain  the  formation  of  the  gas  in  the  Kjeldahl  flask. 
What  third  simple  substance  must  there  be  in  nitric 
acid? 

Note  the  vigor  of  nitric  acid  as  follows.  Put  about 
30CC  of  nitric  acid  in  a  porcelain  evaporating  dish. 
Add  a  piece  of  cloth.  Warm.  Stir  with  a  glass  rod. 
Note  effect  on  cloth.  Stir  the  hot  solution  with  a 
piece  of  wood.  Note  effect  on  wood.  How  do  you 
explain  the  action  on  cloth,  and  on  wood? 

E.     Reaction  of  Nitric  Acid  and  Potassium  Hydroxide. 

Parallel  to  Ex.  30,  F,  except  that  you  use  nitric  acid 
instead  of  sulphuric.  Examine  the  resulting  substance. 
Remembering  the  effect  of  metals  on  the  hydrogen  of 
acids,  state  what  you  think  has  been  the  change  in 
this  case,  also  what  new  substances  have  resulted,  and 
of  what  simple  substances  each  is  composed.  Let  us 
call  the  white  substance  resulting  nitrate  of  potassium. 

Note.  The  substance  resulting  from  the  replacement 
of  hydrogen  in  an  acid  by  a  metal  is  called  a  salt,  e.g., 
sulphates  of  calcium,  magnesium,  zinc,  iron,  etc.,  car- 
bonates of  calcium,  potassium,  etc.,  nitrates  of  sodium, 
potassium,  etc.,  are  all  salts  to  the  chemist,  as  well  as 
chloride  of  sodium.  The  last  we  have  made  by  neutral- 
izing hydrochloric  acid  with  sodium  hydroxide,  as  well 
as  by  the  union  of  chlorine  and  sodium. 

Identify,  by  color,  form,  taste,  flame  coloration,  etc., 
the  nitrate  of  potassium  formed  in  this  experiment  as 
nitre  or  saltpeter. 


68  AMMONIA. 

Finally  answer  our  original  questions.  What  is 
nitre,  and  of  what  simple  substances  composed  ? 
What  is  nitric  acid,  and  of  what  simple  substances 
composed  ? 

To  the  Student.  Up  to  this  point  you  have  worked 
out  everything  by  yourself.  You  have  yourself  proved 
everything  asked.  However  pleasant  it  may  have  been 
to  discover  all  the  truth  for  yourself,  it  is  obviously 
unadvisable  to  proceed  in  this  manner  throughout  your 
work  in  chemistry.  Life  is  too  short  for  you  to  prove 
to  your  own  satisfaction  all  that  has  been  discovered 
by  all  the  workers  in  the  field  of  chemistry  in  all  the 
years.  Now  that  you  have  completed  a  somewhat 
elaborate  chemical  investigation,  and  have  learned  how 
the  pioneers  of  chemistry  attack  their  problems,  you 
are  going  to  be  asked  to  take  much  on  faith,  that  is, 
you  are  going  to  be  asked  to  believe  many  statements 
of  facts  without  stopping  to  verify  all. 


Experiment  33. 

Ammonia. 

A.     Preparation  of  Ammonia. 

Take  the  colorless  oxide  of  nitrogen  of  Ex.  32,  (7, 
and  hydrogen.  Prepare  two  jars  of  this  colorless  oxide 
of  nitrogen  as  in  Ex.  32,  C.  Also  prepare  five  jars  of 
hydrogen  gas,  free  from  air  but  not,  necessarily,  dry. 
Have  ready  in,  a  pail,  or  tub,  of  water  a  bottle  [large 


AMMONIA.  69 

enough  to  hold  all  the  gases J],  inverted,  and  full  of 
water.  Insert  a  large  funnel  in  the  neck  of  the  bottle 
and  pour  the  oxide  of  nitrogen  and  the  hydrogen  up 
into  the  large  hottle.2  Be  careful,  and  do  not  spill  any 
of  the  gases.  The  large  bottle  should  be  fitted  with  a 
two-hole  rubber  stopper.  Through  one  hole  let  a  piece 
of  straight  glass  tube  about  15cm  long  pass,  and  through 
the  other  let  a  piece  of  glass  tube  bent  at  right  angles 
pass  just  through  the  stopper.  The  straight  piece 
should  pass  well  into  the  bottle,  and  each  should  have 
a  few  cm  of  rubber  tube  attached  to  its  outer  end. 
Let  each  rubber  tube  have  a  pinch-cock. 

Remove  the  funnel  from  the  large  bottle,  insert  the 
stopper  with  its  tubes  closed,  and  take  the  bottle  from 
the  pail.  Connect  the  straight  glass  tube,  by  means 
of  its  rubber  tube,  to  the  water  tap.  Connect  the 
bent  glass  tube  to  another  tube  containing  platinum 
sponge  or  platinized  asbestos.  Let  there  be  a  catch- 
bottle  containing  water  put  just  before  the  tube  con- 
taining the  platinum.  Turn  on  the  water,  and  force 
the  gases  through  the  water  of  the  catch-bottle,  and 
note  the  bubbles,  in  order  to  tell  how  fast  the  gases 

1  If  you  have  not  a  bottle  large  enough,  you  can  halve  the  amounts 
of  the  gases  used,  i.e.,  take  one  jar  of  oxide  of  nitrogen,  and  two  and 
one  half  jars  of  hydrogen. 

2  If  you  have  not  the  pail  and  large  funnel,  you  can  proceed  as 
follows.      Take  the  large  bottle  and  pour  into  it  two  jarfuls  of  water. 
Make  a  mark  at  the  height  to  which  the  water  reaches.     Then  pour  in 
five  more  jarfuls,  and  make  another  mark  at  the  height  of  the  seven 
jarfuls  of  water.     Next  fill  the  remainder  of  the  bottle  with  water, 
invert  it  on  the  bridge  of  the  pneumatic  trough,  and  pass  the  two  gases, 
—  first  the  oxide  of  nitrogen,  then  the  hydrogen,  — directly  from  the 
generating  flasks  into  the  bottle,  stopping  the  flow  of  each  when  the 
water  has  fallen  to  the  proper  mark. 


70  AMMONIA   FOUNTAIN. 

are  passing.  Gradually  force  the  mixed  gases  out 
over  the  platinum.  When  the  gases  have  driven  all  the 
air  from  the  catch-bottle,  and  not  before,  heat  the 
platinum.  If  the  heat  is  applied  before  the  air  has 
gone,  there  is  danger  of  an  explosion  in  the  catch- 
bottle.  Why?  Note  the  formation  of  water.  From 
what  is  it  made?  Note  the  formation  of  a  new  gas. 
Note  its  odor  and  action  on  moist  test  papers.  Of 
what  is  it  composed  ?  Let  us  call  it  ammonia.  Pass 
some  of  the  new  gas  into  a  tt  containing  a  little  water, 
and  note  that  the  water  dissolves  the  gas.  Try  the 
action  of  the  water  solution  on  test  papers.  A  water 
solution  of  the  gas  is  sold  in  trade  as  "  aqua  ammonia." 

1>.     Ammonia  Fountain. 

In  order  to  show  the  great  solubility  of  ammonia 
and  the  alkaline  properties  of  aqua  ammonia,  make  an 
ammonia  fountain  as  follows.  Have  ready  two  250CC 
flasks,1  each  fitted  with  a  good  tight  cork.  Arrange  a 
stand  with  a  ring  so  that  one  flask  can  be  supported, 
inverted,  just  above  the  other.  Pass  a  glass  tube 
through  a  hole  in  the  cork  of  the  lower  flask  so  that 
it  reaches  to  the  bottom  of  the  flask  and  projects  about 
an  inch  above  the  cork.  Through  the  cork  in  the 
upper  flask  pass  a  piece  of  tube  drawn  out  to  a  fine 
point  like  the  wash-bottle  tip.  The  opening  of  the  tip 
should  have  a  diameter  not  less  than  lmm  and  not  more 
than  2mm.  The  tip  should  end  at  about  the  middle  of 
the  upper  flask.  Connect  the  glass  tubes  by  a  rubber 
connector.  Bore  a  second  hole  in  the  cork  of  the  lower 

1  Kjeldahl  are  best  because  they  can  stand  more  pressure  without 
breaking  than  can  ordinary  flasks. 


SALTS    OF   AMMONIUM.  71 

flask  and  pass  a  bit  of  glass  tube  bent  at  a  right  angle 
through  it  to  admit  air.  Fill  the  lower  flask  one  half 
or  two  thirds  full  of  water.  Add  enough  red  [acid] 
solution  of  litmus  to  color  the  water  distinctly  red. 
Take  the  upper  flask  from  its  support,  and  fill  it  full 
of  ammonia.  Best  prepare  the  ammonia  by  putting 
about  50CC  of  commercial  aqua  ammonia  in  a  flask  and 
heating  to  drive  off  the  gas.  Conduct  the  gas  into  the 
flask  by  a  rubber  tube.  Ammonia  is  a  light  gas  com- 
pared with  air.  Get  the  flask  full  of  ammonia  gas. 
At  once  insert  the  cork  and  put  the  flask  in  position. 
Then  connect  with  the  lower  flask.  Blow,  a  little,  in 
the  air  vent  of  the  lower  flask  to  start  the  fountain. 
Step  back,  as  the  flask  may  burst  from  the  violence  of 
the  action.  Note  phenomena  [physical  and  chemical]. 
Explain. 

C.     Salts  of  Ammonium. 

What  is  a  salt,  chemically?  How  have  we  made 
salts? 

An  aqueous  solution  of  ammonia  behaves  much  like 
an  aqueous  solution  of  sodium  [or  potassium]  hydroxide. 
It  is  alkaline  to  test  papers,  and  will  react  with  acids 
and  form  white  salt-like  substances  ;  in  fact,  it  seems 
as  though  hydrogen  and  nitrogen  together  act  like  a 
metal.  When  thus  acting  together  they  are  given  the 
name  of  ammonium.  Thus  aqua  ammonia  is  con- 
sidered a  solution  of  ammonium  hydroxide. 

1.    CHLORIDE  OF  AMMONIUM. 

Neutralize  about  10CC  of  aqua  ammonia  [diluted  with 
30CC  of  water]  with  hydrochloric  acid,  —  also  diluted. 


72  OXIDES    OF   NITROGEN. 

Evaporate  to  crystallization.  Examine  the  product. 
What  shall  we  call  it?  Put  a  little  of  this  product 
in  the  bottom  of  a  dry  tt.  Heat  gently.  Note  subli- 
mate on  the  sides  of  the  tt.  What  is  sublimation  ? 

2.    SULPHATE  OF  AMMONIUM. 

Make    this    substance,    and    describe    it.       Will    it 

sublime  ? 

3.    NITRATE  OF  AMMONIUM. 

Make  this  substance,  and  describe  it. 


Experiment  34. 
Oxides   of  Nitrogen. 

Note  that  we  have  already  made  two  oxides  of 
nitrogen :  one  a  colorless  gas,  the  other  a  brown  gas. 
Review  "A  Chemical  Investigation,"  Part  (7,  and  now 
state  the  proportion  of  oxygen  to  nitrogen  [by  volume] 
in  the  first,  or  colorless,  oxide  of  nitrogen.  What  can 
you  say  in  regard  to  the  amount  of  oxygen  in  the 
second,  or  brown,  oxide,  compared  with  the  amount 
in  the  first? 

There  are  other  compounds  known  which  contain 
nitrogen  and  oxygen  only.  Of  these  perhaps  the  most 
interesting  is  the  so-called  nitrons  oxide  or  laughing- 
gas.  Nitrous  oxide  is  best  prepared  by  decomposing 
ammonium  nitrate  by  heat.  Water  and  laughing  gas 
are  the  products  of  this  decomposition. 

Take  about  10g  of  ammonium  nitrate.  Heat  this 
gently  in  a  large  tt  fitted  with  a  one-hole  cork  and  a 


OXIDES   OF   NITROGEN.  73 

delivery  tube.  Conduct  the  gases  through  three  catch- 
bottles.  Let  the  first  catch-bottle  contain  no  liquid, 
but  be  kept  cold  to  condense  the  water  formed  in  the 
decomposition  of  the  nitrate.  Let  the  second  catch- 
bottle  contain  a  little  aqueous  solution  of  hydroxide 
of  sodium,  to  catch  any  acid-forming  fumes.  Let  the 
third  catch-bottle  contain  a  little  aqueous  solution  of 
sulphate  of  iron,  to  catch  any  of  the  [harmful]  color- 
less nitric  oxide  that  may  be  formed  as  a  by-product. 
These  by-products  are  most  apt  to  be  formed  if  the 
heat  is  applied  too  suddenly  to  the  nitrate,  or  if  the 
temperature  is  allowed  to  rise  much  above  170°  C. 

As  nitrous  oxide  is  soluble  in  cold  water,  the  end 
of  the  delivery  tube  from  the  last  catch-bottle  should 
dip  beneath  the  surface  of  some  warm  water,  in  a  beaker 
or  other  vessel,  and  not  into  the  cold  water  of  a  pneu- 
matic trough.  Catch  the  nitrous  oxide  in  large  tts. 
Get  its  properties.  Particularly  test  it  with  a  large 
glowing  splinter  of  wood.  Does  it  oxidize  to  a  brown 
second  oxide  on  exposure  to  the  air,  as  did  the  first  oxide 
of  nitrogen  you  made  ?  Inhale  a  little  nitrous  oxide. 

Nitrous  oxide  has  a  greater  proportion  of  nitrogen 
than  does  the  first  oxide  of  nitrogen  you  made.  What 
proportion  did  you  prove  the  first  oxide  has?  That 
oxide  is  called  nitric  oxide.  Compare  the  names 
sulphurous  and  sulphurzV,  as  applied  to  oxides  and 
acids  of  sulphur. 


Note.  At  this  point,  before  going  on  with  Part  II,  the  student 
should  re-read  carefully  the  Introduction  to  this  book,  and  take 
note  whether  or  not  he  has  been  following  the  suggestions  there 
made. 


PART   II. 


ADDITIONAL    EXPERIMENTS. 


PART   II.  — ADDITIONAL   EXPERIMENTS. 


Experiment  1. 

Bromine. 

EXAMINE  a  small  amount  of  bromine  and  get  its 
chief  properties.  Do  not  breathe  in  more  than  the 
least  bit  of  bromine,  for  this  substance  is  very  bad 
for  the  mucous  membranes. 

Note  particularly  state,  color,  odor,  volatility,  and 
effect  on  moist  test  papers.  To  observe  the  properties 
it  is  best  to  take  the  bromine  bottle  to  the  hood,  and 
with  the  window  pulled  so  as  to  admit  the  arms  only, 
pour  a  single  drop  of  bromine  into  a  tt  and  examine 
at  leisure.  On  no  account  let  a  drop  of  bromine  touch 
the  flesh,  as  it  makes  a  corrosive  sore.  Add  about  5CC 
of  water  to  a  tt  full  of  bromine  vapors.  Shake.  Note 
solubility.  Warm,  and  note  effect.  Do  this  last 
experiment  under  a  hood.  Again  prepare,  in  a  tt, 
about  5CC  of  bromine  water.  Add  about  2CC  of  ether. 
[Caution!  Ether  is  dangerously  inflammable.  Have 
no  fire  near.]  Shake.  Note  the  solubility  of  bromine 
in  ether  as  compared  with  its  solubility  in  water.  Note 
color  of  bromine  solution  in  ether.  Note  also  how 
slightly  ether  mixes  with  water.  Is  ether  heavier  or 
lighter  than  water?  Try,  in  a  similar  way,  the  solu- 
bility of  bromine  in  sulphide  of  carbon.  [Caution ! 


78  BROMIDES. 

Sulphide  of  carbon  also  is  dangerously  inflammable. 
Have  no  fire  near.]  Note  the  color  of  the  solution 
of  bromine  in  sulphide  of  carbon. 


Experiment  2. 
Bromides. 

Hydrogen  unites  with  bromine,  but  not  so  vigorously 
as  with  chlorine.  By  passing  the  vapors  of  bromine 
and  hydrogen  gas  over  hot  platinum  sponge  the  union 
may  be  made.  The  resulting  hydrogen  bromide  is 
much  like  hydrochloric  acid.  It  is  also  very  soluble 
in  water,  and  is  commonly  used  in  aqueous  solution. 

A.  Properties  of  Hydrogen  Bromide. 
Take  about  lcc  of  aqueous  hydrobromic  acid  in  a  tt, 
and  get  the  properties  both  of  the  liquid  and  of  the 
gaseous  bromide  of  hydrogen  that  may  be  evolved  by 
warming  the  liquid.  Compare  especially  with  hydro- 
chloric acid. 

B.     Sodium  Bromide. 

Neutralize  about  lcc  of  hydrobromic  acid  solution  with 
sodium  hydroxide  —  or  sodium  carbonate  —  solution. 
Evaporate  to  dryness.  Examine  the  product.  Get  the 
chief  properties  of  the  sodium  bromide.  Compare  it 
with  table  salt,  e.g.,  in  color,  form,  and  taste. 

C.     Replacement  of  Bromine,  in  a  Bromide,  by  Chlorine. 
Make,  in  a  tt,  a  solution  of  10CC  of  water  and  O.lg 
of  bromide  of  potassium.     Add  about  5CC  of  chlorine 


IODIN 

water,  i.e.,  water  which  has  dissol 
Add  about  lcc  of  sulphide  of  carbon.  Why  add  the 
sulphide  of  carbon?  Shake.  Note  effect.  What  has 
happened  ? 

Experiment  3. 
Iodine. 

A.  Properties  of  Iodine. 

Examine  a  crystal  of  iodine  and  get  its  chief  proper- 
ties. Note  particularly  state,  color,  solubility,  and  color 
of  vapor.  To  note  the  last,  have  ready  a  tt  Jfefot  at  the 
lower  end.  Drop  in  a  crystal  of  iodine  and  examine 
the  vapor. 

B.  Solubility  of  Iodine. 

Get  the  relative  solubility  of  iodine  in  the  following 
solvents  :  —  water,  alcohol,  ether,  and  sulphide  of  car- 
bon. Caution !  Remember  that  alcohol  and  ether,  as 
well  as  sulphide  of  carbon,  are  dangerously  inflammable. 
Have  no  fire  near.  Save,  for  (7,  the  alcohol  solution, 
which  is  called  tincture  of  iodine. 

C.     Action  of  Iodine  on  the  Skin. 

Drop  a  small  drop  of  iodine  solution,  saved  from  B, 
on  the  skin.  Note  effect. 

D.     Action  of  Iodine  on  Starch. 

Prepare  some  starch  paste  as  follows  :  Have  ready 
in  a  porcelain  evaporating  dish  50CC  of  boiling  water. 

1  Chlorine  water  may  be  made  by  allowing  chlorine  gas  to  bubble  up 
through  cold  water  contained  in  a  catch-bottle,  flask,  or  other  vessel. 


80  IODIDES. 

Rub  in  a  mortar  lg  of  starch  and  a  few  drops  of  water 
to  the  consistency  of  cream.  Stir  the  starch  into  the 
boiling  water  and  set  aside. 

Put  in  a  tt  about  lcc  of  water,  add  two  or  three  drops 
of  starch  paste,  then  add  [after  shaking  till  the  paste  is 
well  mixed  with  the  water]  a  single  drop  of  an  aqueous 
solution,  or  a  minute  crystal,  of  iodine.  Heat  the  solu- 
tion and  note  the  effect.  Cool,  and  note  again.  Dip  a 
strip  of  filter  paper  in  the  starch  paste  and  suspend  it 
across  the  mouth  of  a  tt  containing  a  small  crystal  of 
iodine  in  the  bottom.  Note  effect.  What  does  this  show  ? 


Experiment  4. 
Iodides. 

Hydrogen  unites  with  iodine,  but  not  readily.  By 
using  platinum  sponge  and  iodine  vapors  the  union 
may,  with  difficulty,  be  made.  Hydrogen  iodide,  or 
hydriodic  acid,  as  it  is  usually  called,  resembles  hydro- 
chloric and  hydrobromic  acids.  It  forms  iodides  similar 
to  bromides  and  chlorides. 

A.     The  Properties  of  Potassic  Iodide. 

Examine  this  substance.  Note  its  chief  properties. 
State  what  relation  it  has  to  hydriodic  acid,  to  bromide 
of  potassium,  to  chloride  of  potassium. 

B.    Replacement  of  Iodine  by  Chlorine. 
Make  a  solution,  in  a  tt,  of  10CC  of  water  and  O.lg  of 
iodide  of  potassium.     Add  about  5CC  of  chlorine  water. 
Then  about  lcc  of  sulphide  of  carbon.  Shake.  Note  effect. 


FLUORINE    AND    FLUORIDES.  81 

Stir  a  crystal  of  potassic  iodide  into  a  starch  solution. 
Note  effect.  Add  a  few  drops  of  chlorine  water.  Note 
effect.  Explain. 

C.     Will  Bromine  Displace  Iodine? 

Perform  an  experiment  to  prove  which  has  the 
stronger  attraction  for  potassium  --  iodine  or  bro- 
mine. Record  details  of  the  experiment,  and  the 
conclusion  reached. 


Experiment  5. 

Fluorine  and  Fluorides. 

We  have  studied  iodine,  bromine,  chlorine,  and  the 
corresponding  iodides,  bromides,  and  chlorides.  It  has 
long  been  known  that  there  must  be  a  fourth  member 
of  this  halogen  1  group,  because  salts  were  known  — 
called  fluorides  —  similar  to  the  bromides,  chlorides, 
and  iodides.  The  simple  substance  itself  has  recently 
been  prepared  and  is  called  fluorine.  Fluorine  is 
much  like  chlorine,  but  acts  more  energetically. 

A.     The  Properties  of  Calcic  Fluoride. 

Examine  some  fluoride  of  calcium  and  get  its  chief 
properties. 

B.     Preparation  of  Fluoride  of  Hydrogen. 

Compare  the  "  preparation  of  hydrochloric  acid  on  a 
large  scale,"  Ex.  29,  C.     Put  about  lg  calcic  fluoride 

1  Halogen  means  salt-making.     Note  that  chlorine  makes  common 
gait,  and  bromine  and  iodine  similar  salts, 


82  HYDROFLUORIC    ACID. 

in  a  tt.  Add  enough  sulphuric  acid  to  make  a  paste. 
Warm  gently.  Smell  cautiously.  A  small  amount  of 
this  gas  can  seriously  injure  the  lungs.  Hold  a  glass 
rod  wet  with  water  in  the  mouth  of  the  tt.  Get  the 
chief  properties  of  hydrofluoric  acid. 

C.     Etching  of  Glass  by  Hydrofluoric  Acid. 

Hydrogen  fluoride  is  an  extremely  corrosive  sub- 
stance. All  metals,  except  lead,  gold,  and  platinum, 
act  with  it  to  form  metallic  fluorides.  Even  glass  is 
eaten  away  by  hydrogen  fluoride,  with  the  formation 
of  silicon  fluoride,  the  silicon  coming  from  the  sand 
which  was  used  to  make  the  glass.  Hence  hydrofluoric 
acid  cannot  be  kept  in  a  glass  bottle.  It  can  be  kept 
in  lead,  platinum,  or  rubber. 

Warm  a  bit  of  glass,  e.g.,  the  bottom  of  a  beaker  or 
of  a  crystal  pan,  and  drop  on  it  a  little  wax  or  candle 
grease.  Spread  the  grease  thin,  and  let  it  harden  by 
cooling.  Then  trace  some  figure  or  name  in  the  grease, 
cutting  through  to  the  glass.  Generate  hydrogen  fluo- 
ride again,  as  in  .5,  using  for  a  generating  vessel  a 
small  beaker,  a  large  tt,  or,  still  better,  a  lead  dish. 
Expose  the  prepared  glass  to  the  action  of  the  vapors 
of  hydrogen  fluoride  for  a  few  minutes.  Do  not  melt 
the  grease  while  the  vapors  are  acting.  Then  warm 
the  glass,  to  melt  the  grease,  and  wipe  off  the  grease 
with  filter  paper.  Examine  the  surface  of  the  glass. 
Breathe  on  it.  What  do  you  note  ?  Explain. 


ARSENIC    AND    ITS    COMPOUNDS.  83 

Experiment  6. 

Arsenic  and  its  Compounds. 

Caution !  In  all  your  work  with  arsenic  and  its 
compounds  use  extreme  care,  and  do  not  get  poisoned. 

A.     The  Properties  of  the  Simple  Substance  —  Arsenic. 

Examine  a  small  bit  of  arsenic  and  note  its  chief 
properties.  Keep  it  well  away  from  the  mouth.  Do 
not  test  its  chemical  properties  without  the  advice  of 
the  instructor.  Put  a  piece,  not  larger  than  a  common 
pin's  head,  in  a  hard  glass  bulb  tube,  clean  and  dry, 
with  a  long  stem.  Heat  gently.  Note  effect.  Be  sure 
you  put  the  tube  when  used  [and  all  remnants  of 
arsenic  and  arsenic  compounds]  in  a  small  waste-box 
provided  for  the  purpose.1 

B.     Oxidation  of  Arsenic. 

Do  this  under  a  hood  with  window  pulled  down. 
Burn,  on  the  cover  of  a  porcelain  crucible,  a  bit  of 
arsenic,  not  larger  than  a  pin's  head.  Note  the  oxide 
formed.  This  white  oxide  is  the  "white  arsenic," 
or,  more  commonly,  "arsenic,"  of  the  apothecaries. 
Describe  it. 

Again  burn  arsenic  [the  smallest  possible  amount] 
in  order  to  get  the  peculiar  odor  of  the  oxide.  Note 
that  it  has  a  garlic  odor,  and  reminds  one  of  onions. 

1  These  arsenic  residues  should  not  be  thrown  with  the  other  labora- 
tory waste,  but  should  be  guarded  from  contact  with  chemicals. 


84  OXIDE   OF   ARSENIC. 

C.    Reduction  of  the  Oxide  of  Arsenic. 

Carbon  has  the  power  of  removing  the  oxygen  from 
this  oxide.  Compare  the  removal  of  oxygen  from  the 
non-combustible  oxide  of  carbon  by  means  of  zinc. 
Fill  the  bulb  of  a  hard  glass  matrass  half  full  of  a 
mixture  of  equal  parts  of  powdered  charcoal  and  oxide 
of  arsenic.  Warm  gently.  Note  arsenic  mirror.  Is 
all  the  oxygen  taken  irom  the  arsenic,  or  is  a  lower 
oxide  left  as  in  the  case  of  the  reduction  of  the  dioxide 
of  carbon? 

/>.     Arsenide  of  Hydrogen. 

Caution !  Arsenide  of  hydrogen  is  one  of  the  most 
poisonous  substances  known.  Use  every  care. 

Arsenic,  like  sulphur,  forms  a  gaseous  compound 
with  hydrogen,  similar  to  the  sulphide  of  hydrogen. 
The  arsenic  compound  is  called  arsenide  of  hydro- 
g-en,  or  arsine,1  and  is  characterized  by  its  frightfully 
poisonous  nature.  Take  a  small,  e.g.,  a  2  oz.  or  a  4  oz. 
salt-mouth  bottle.  Fit  with  a  two-hole  rubber  stopper. 
Pass  a  funnel-tube  through  one  hole  and  nearly  to  the 
bottom  of  the  bottle.  Through  the  other  hole  pass  a 
short  right-angled  piece  of  glass  tube.  The  inner  end 
of  this  glass  tube  should  be  flush  with  the  smaller  end 
of  the  rubber  stopper.  With  the  right-angled  tube, 
connect  a  tube  containing  chloride  of  calcium  in  small 
lumps.  What  is  a  chief  property  of  chloride  of  cal- 
cium? Connect  with  the  chloride  of  calcium  tube  a 
piece  of  hard  glass  tube  drawn  to  a  pin-hole  bore  and 
turned  up  at  a  right-angle,  similar  to  the  tube  used 

1  Also  called  arseniuretted  hydrogen. 


DETECTION    OF    ABSENIC.  85 

for  the  production  of  hydrogen  sulphide,  Ex.  23,  B. 
Put  in  the  bottle  about  5g  of  c.p.1  zinc,  and  a  few 
cc  of  c.p.  sulphuric  acid,  diluted,  e.g.,  1  vol.  acid  to 
5  vols.  of  water.  Let  the  hydrogen  evolved  pass 
through  the  tubes  till  all  the  air  is  removed  and  till 
the  gas  can  be  lighted  [by  the  explosion  tube]  when 
it  issues  from  the  turned-up  small  glass  tube.  When 
the  hydrogen  is  burning  well,  place  the  flame  of  a 
Bunsen  burner  under  the  hard  glass  tube  just  before 
the  point  where  it  narrows  to  a  pin-hole  size.  Do 
not  remove  this  flame  till  the  experiment  is  finished. 
Then  add,  through  the  funnel-tube,  to  the  bottle  five 
drops,  and  no  more,  of  an  arsenical  solution.  Use  the 
arsenical  solution  especially  prepared  by  the  instructor 
for  this  purpose  and  no  other  solution.2  Wash  the 
whole  of  the  solution  used  down  the  funnel  tube  into 
the  bottle  by  means  of  pure  water  from  the  wash-bottle. 
Continue  the  heating  for  30  minutes  at  least.  The 
hydrogen  of  the  sulphuric  acid  joins  the  arsenic  and  the 
arsenide  of  hydrogen  passes  off.  Compare  the  forma- 
tion of  sulphide  of  hydrogen.  The  gas  is  decomposed 
as  it  passes  through  the  hot  tube,  and  the  hydrogen 
passes  on  and  burns,  while  the  arsenic  is  left,  as  a 
mirror,  in  the  contracted  tube.  Compare  the  action 
of  heat  on  sulphide  of  hydrogen.  Keep  the  arsenic 
mirror  for  future  work. 

E.     Detection  of  Arsenic. 

D  gives  us  a  method  for  detecting  arsenic.      It  is 
always  necessary  first  to  make  sure  that  the  arsenic 

1  In  chemistry,  c.p.  stands  for  chemically  pure. 

2  See  Appendix  J. 


86  DETECTION    OF    ARSENIC. 

is  in  such  a  form  that  the  hydrogen  can  join  it  and 
form  the  arsenide  of  hydrogen.  Therefore  the  sub- 
stance which  you  suspect  contains  arsenic  should  first 
be  treated  with  sulphuric  acid  [or,  in  the  case  of  a 
piece  of  cloth,  carpet,  or  other  substance  likely  to 
contain  wool,  with  nitric  and  sulphuric  acids]. 

Arrange  the  apparatus  as  in  D.  Start  the  hydrogen, 
and  when  safe  to  light  the  jet  do  so,  and  put  the  Bunsen 
burner  in  place.  Allow  the  hydrogen  alone  to  pass  for 
15  minutes  with  the  tube  at  a  dull  red.  This  prelim- 
inary test  is  to  make  sure  that  there  is  no  arsenic  in  the 
zinc  or  the  acid  used,  and  none  left  from  a  previous 
experiment. 

Cut  from  a  piece  of  wall  paper,  or  any  similar  sus- 
pected material  supposed  to  contain  arsenic,  one  square 
decimeter.  Be  sure  you  include  all  the  colors  of  the 
figures,  if  the  material  is  figured.  Tear  the  substance 
in  small  bits  and  put  these  in  a  clean  and  dry  porcelain 
evaporating  dish.  Add  a  little  c.p.  sulphuric  acid. 
Warm  gently,  and  stir  with  a  glass  rod  till  solution 
takes  place.  The  solution  will  not  be  transparent, 
and  is  generally  black.  Do  not  use  enough  acid  to 
make  the  solution  really  liquid  —  it  should  be  some- 
what pasty.1  Add  about  20CC  of  cold  water,  or  an  equal 
weight  of  ice  or  snow,  to  dilute  the  strong  acid.  When 
cool,  filter.  The  arsenical  solution  runs  through.  If 
there  is  any  precipitate,  wash  this  a  little  and  add  the 
washings  to  the  filtrate.  If  the  apparatus  has  shown 

1  If  the  substance  contains  wool  its  sulphur  must  now  be  oxidized. 
Add  to  the  sulphuric  acid  solution  about  5CC  of  c.p.  nitric  acid.  Evap- 
orate till  white  fumes  appear.  Repeat  this  treatment.  Then  dilute 
with  water,  again  evaporate  till  white  fumes  appear,  and  go  on  as  above. 


ANTIMONY.  87 

no  arsenic  after  the  preliminary  test  of  15  minutes, 
add  the  solution  to  be  tested  through  the  funnel.  Be 
careful  and  do  not  let  many  bubbles  of  air  go  down  the 
funnel-tube  with  the  solution.  If  arsenic  now  appears 
the  experiment  should  be  continued  for  30  minutes  in 
order  to  catch  all  the  arsenic  as  a  mirror.  Caution! 
If  arsenic  appears,  do  not  break  any  joints  of  the  appa- 
ratus, nor  remove  the  Bunsen  burner,  for  30  minutes, 
or  there  will  be  danger  of  being  poisoned  by  the  escap- 
ing arsenide  of  hydrogen.  It  is  also  well  to  keep  the 
little  jet  of  hydrogen  burning  all  the  time  to  decompose 
any  hydrogen  arsenide  that  may  escape  the  decompo- 
sition above  the  Bunsen  burner.  If  the  wind  blows  the 
flame  of  the  Bunsen  burner,  protect  it  with  a  book,  or 
something  else,  or  the  arsine  may  escape  undecomposed. 


Experiment  7. 
Antimony,     [Stibium.] 

In  doing  this  experiment  note  the  similarity  between 
antimony  and  arsenic. 

A.     The  Properties  of  Antimony. 

Get  the  chief  properties  of  antimony.     Try  sublim- 
ing some  in  a  small  matrass. 

B.     Oxidation  of  Antimony. 

To  oxidize  it  well,  heat  it  on  a  crucible  cover  before 
a  small  mouth  blow-pipe.     Place  on  the  cover  a  piece 


88  HYDRIDE    OF    ANTIMONY. 

of  antimony  as  large  as  a  pin's  head.  Using  a 
Bunsen  burner,  direct  the  blow-pipe  flame 1  against 
the  antimony.  Note  the  fumes  of  oxide  that  rise. 
Suddenly  stop  the  blast,  and  note  the  globule  of 
molten  antimony  as  it  becomes  coated  with  oxide. 
Drop  a  small  molten  globule  of  antimony  from  some 
height  down  on  a  piece  of  paper  whose  edges  are 
turned  up  [to  prevent  the  antimony  running  off], 
and  note  effect. 

C.  Chloride  of  Antimony. 

Take  a  jar  of  chlorine.  Sift  in  a  little  antimony, 
which  has  been  ground,  in  a  mortar,  to  the  finest 
possible  powder.1  Note  the  phenomena,  and  examine 
the  compound  formed.  Review  the  formation  of  table 
salt. 

D.  Hydrogen  Antimonide. 

Treat  a  solution  of  some  antimony  compound2  in 
the  apparatus  used  in  Ex.  6,  D.  Hydrogen  joins  the 
antimony,  and  gaseous  antimoiiide  of  hydrogen  results. 
Examine  the  antimony  mirror,  and  compare  it  with 
the  arsenic  mirror,  particularly  as  to  position  in  the 
tube,  color,  and  lustre.  Heat  each  gently,  and  see 
which  sublimes  easier.  Prepare  a  solution  of  bleach- 
ing lime  [about  1  part  lime  to  10  of  water]  and 
dip,  alternately,  the  mirrors  in  this  solution.  Which 
dissolves  the  easier  ? 

1  For  use  of  blow-pipe,  see  Appendix  K. 

2  See  Appendix  J,  2. 


BISMUTH.  89 


E.     A  Chemical  Examination. 

Examine  two  pieces  of  paper,1  one  containing  arsenic, 
the  other  antimony.  Compare  the  two  mirrors  which 
you  get,  and  determine  which  is  arsenic  and  which  is 
antimony. 


Experiment  8. 

Bismuth. 

A.     The  Properties  of  Bismuth. 

Examine  a  small  piece  of  the  metal  and  get  its  chief 
properties. 

B.     Nitrate  of  Bismuth. 

Prepare  nitrate  of  bismuth  by  putting  a  lump  of 
bismuth  in  a  small  amount  of  nitric  acid.  Heat 
somewhat.  Add  to  this  nitrate  about  lcc  of  water. 
Note  solubility.  Then  add  the  solution  to  100CC  of 
water  and  note  the  formation  of  a  basic  nitrate,  insol- 
uble in  water,  which  settles  out  as  a  light  milky 
precipitate. 


Experiment  9. 

Tin.     [Stannum.] 
A.     The  Properties  of  Tin. 

Examine  tin  in  various  forms,  e.g.,  bar,  granular,  foil, 
and  on  iron  as  "tin  plate."     Get  the  chief  properties 
of  tin,  noting  particularly  its  color,  lustre,  hardness, 
1  See  Appendix  L. 


90  TIN   COMPOUNDS. 

"cry,"  and  whether  it  is  much  or  little  affected  by 
water  and  the  air.  To  note  its  cry,  bend  a  bar  or 
pinch  it  between  the  teeth. 

B.     Oxidation  of  Tin. 

Oxidize  granular  tin  in  a  small  Hessian  crucible 
over  a  blast-lamp,  or  in  a  Fletcher  furnace.  Stir  often. 
Examine  the  oxide  and  get  its  chief  properties. 

C.     Crystalline  Structure. 

Take  a  piece  of  "scrap  tin  plate,"  i.e.,  a  bit  of  tinned 
iron  that  has  been  cut  off  in  the  making  of  tin  ware. 
Heat  this  over  the  Bunsen  burner  flame  till  the  tin 
begins  to  run.  Plunge  into  cold  water  suddenly. 
Remove  the  superficial  oxidation  by  rubbing  the  sur- 
face with  a  bit  of  filter  paper  wet  in  nitric  and  hydro- 
chloric acids.  Remove  the  acids  by  rubbing  with  a 
weak  solution  of  sodium  hydroxide.  Wash  off  the 
sodium  hydroxide  with  water.  Examine  the  crystal- 
line structure  presented  by  the  tin. 

D.     Action  of  Strong  Acids  on  Tin. 

1.  Treat  tin,  in  a  tt,  with  hydrochloric  acid  —  cold 
and  hot. 

2. .  Treat  tin,  in  a  tt,  with  sulphuric  acid  —  cold  and 
hot. 

3.    Treat  tin,  in  a  tt,  with  nitric  acid  —  cold  and  hot. 

Note  effect  in  each  case.     Save  substances  formed. 


LEAD.  91 

E.     Replacement  of  Tin  by  Zinc. 

Use  the  chloride  of  tin  made  in  D.  Make  a  strong 
solution  of  chloride  of  tin.  Put  this  in  a  large  tt. 
Clean  a  narrow  strip  of  zinc  and  insert  it  in  the 
solution.  Note  effect.  Explain. 


Experiment  1O. 

Lead.     [Plumbum.] 

A.     The  Properties  of  Lead. 

Examine  a  piece  of  lead  and  note  the  chief  properties. 
B.     Oxidation  of  Lead. 

Put  some  lead  in  a  Hessian  crucible  and  heat  it  over 
the  blast^lamp.  Stir  to  admit  air.  Note  that  the  lead 
forms  several  oxides  of  different  colors.  Do  not  let  the 
heat  become  very  great.  Save  some  oxide. 

C.     Action  of  Water  on  Oxide  of  Lead. 

In  a  mortar  grind  a  little  of  the  oxide  of  lead,  from 
B,  with  about  5CC  of  water.  Filter  and  see  if  anything 
has  gone  into  solution.  Test  the  liquid  also  with  test 
papers.  State  what  you  can  about  this  experiment 
from  a  chemical  point  of  view,  —  from  a  sanitary  point 
of  view,  e.g.,  in  reference  to  the  use  of  lead  pipes  for 
conveying  drinking  water,  inasmuch  as  soluble  com- 
pounds of  lead  are  poisons. 

D.     Action  of  Acids  on  Lead. 
Similar  to  9,  D.     Record  results  in  tabular  form. 


92  LEAD   COMPOUNDS. 

E.     Replacement  of  Lead  by  Zinc. 

Similar  to  9,  jK,  except  a  solution  of  lead  nitrate 
best  be  used.  Note  the  formation  of  a  "  lead  tree." 
Explain. 

F.  Lead  Chloride. 

Treat  a  strong  solution  of  5g  of  lead  nitrate  with  an 
excess  of  hydrochloric  acid.  Explain  the  replacement 
that  takes  place.  Dilute  a  little  and  filter.  While  the 
precipitate  of  lead  chloride  is  still  on  the  filter,  wash  it 
a  little  with  a  stream  from  the  wash-bottle.  Get  its 
chief  properties.  Put  the  precipitate  of  lead  chloride 
in  a  tt.  Add  three  times  its  volume  of  cold  water. 
Warm.  Note  solubility  in  hot  water.  Let  the  solution 
cool,  and  note  the  formation  of  crystals. 

G.  Lead  Sulphate. 

Compare  the  results  of  D  for  the  action  of  sulphuric 
acid  on  lead  itself.  Now  prepare  lead  sulphate  by 
adding  sulphuric  acid  to  a  solution  of  lead  nitrate. 
Wash  the  precipitate,  as  in  F,  and  get  its  chief  prop- 
erties. Note  that  this  is  a  roundabout  way  for  prepar- 
ing a  salt  when  we  cannot  readily  get  it  by  treating 
the  metal  with  the  acid.  Such  roundabout  methods 
are  often  used  by  the  chemist. 

H.     Plumbers'  Solder. 

Melt,  in  a  Hessian  crucible,  equal  parts  of  tin  and 
lead.  The  resulting  alloy  is  common  solder.  Note 
how  much  more  easily  solder  may  be  melted  than  either 


SILVER.  93 

lead  or  tin.     Two  or  more  metals  thus  fused  together 
form  what  is  called  an  alloy. 

I.     Fusible  Alloy. 

Take  15g  of  bismuth,  8g  of  tin,  and  8g  of  lead.  Put 
each  under  boiling  water,  and  note  that  no  one  of  them 
melts.  Dry  the  metals,  and  fuse  the  three  together  in 
an  iron  spoon  or  a  crucible  ;  cool,  and  place  the  alloy 
thus  produced  in  boiling  water.  Note  effect.  While 
still  melted,  pour  the  alloy  into  a  narrow,  thin-walled 
tt.  Let  cool.  Note  effect.  Explain. 


Experiment  11. 

Silver.     [Argentum.] 

A.    The  Properties  of  Silver. 

Examine  a  small  piece  of  silver  and  note  its  chief 
properties,  particularly  the  effect  of  air  and  water  on  it. 

B.     Oxidation  of  Silver. 

Attempt  to  form  an  oxide  of  silver  in  all  the  ways 
you  know  for  oxidation. 

C.    Action  of  Acids  on  Silver. 

Try  your  strongest  acids  —  sulphuric,  hydrochloric, 
and  nitric  —  "in  the  cold "  l  and  when  hot.  Evaporate 
some  of  the  acid  after  each  attempt,  and  compare  the 

I  This  expression  means  at  ordinary  temperature, 


94  SILVER. 

amounts  of  residue.  Try  dilute  and  strong  acids. 
Save  any  salts  found.  Make  a  carefully  prepared 
table  of  results. 

D.     Replacement  of  Silver  by  Copper. 

Take  0.5g  of  silver  nitrate,  dissolve  it  in  10CC  of 
water.  Add  a  freshly  cleaned  strip  of  copper.  Note 
effect.  Spread  the  silver  on  a  hard  surface  and  rub 
it  with  some  hard  instrument,  as  a  knife  blade,  to 
restore  its  lustre. 

K.     Replacement  of  Silver  by  Calcium,  Sodium,  and 
Potassium. 

1.  Replacement  of  silver  by  calcium,  and  the  forma- 
tion of  silver  chloride. 

Put  a  small  crystal  of  nitrate  of  silver  in  about  10CC 
of  water.  Shake  till  solution  takes  place.  Have  ready 
a  solution  of  a  small  lump  of  calcic  chloride  in  about 
10CC  of  water.  Mix  the  solutions.  Filter.  Examine 
the  precipitate  of  silver  chloride.  Expose  some  to  light 
—  sunlight  is  best.  Note  effect.  Explain  the  changes. 
Name  the  factors  and  the  products.1 

2.  Replacement  of  silver  by  sodium,  and  the  forma- 
tion of  silver  bromide. 

Proceed  as  in  1,  but  use  sodic  bromide  for  calcic 
chloride. 

3.  Replacement  of  silver  by  potassium,  and  the  for- 
mation of  silver  iodide. 

1  After  every  experiment  in  which  silver  or  silver  nitrate  is  used, 
any  residues  (solid  or  liquid)  containing  silver  should  be  saved.  When 
a  considerable  quantity  of  these  residues  has  been  obtained,  the 
instructor  should  regain  the  silver  from  them.  See  II,  Method  II. 


PURIFICATION    OF    SILVER.  95 

Proceed  as  in  1,  but  use  potassic  iodide  for  calcic 
chloride. 

F.     Sulphide  of  Silver. 

Dissolve  a  small  crystal  of  nitrate  of  silver  in  a  tt 
half  full  of  water.  Generate  sulphide  of  hydrogen 
[from  sulphide  of  iron  and  dilute  sulphuric  acid  in  a 
flask  or  in  a  tt],  and  pass  the  gas  through  the  nitrate 
solution  in  the  tt.  Examine  the  sulphide  of  silver 
formed.  Explain  the  replacement  that  has  caused  the 
formation  of  silver  sulphide.  What  is  left  in  solution  ? 
Hold  a  silver  coin  for  a  moment  in  a  stream  of  sul- 
phuretted hydrogen.  Note  effect. 

G.     Oxide  of  Silver. 

Add  about  0.5g  of  nitrate  of  silver  to  half  a  tt  of 
water.  Then  add  a  few  drops  of  a  strong  solution  of 
sodium  hydroxide.  Examine  the  silver  oxide  formed. 
Explain  the  chemical  changes. 

H.     Purification  of  Silver. 
METHOD  I.     BY  REPLACEMENT  WITH  COPPER. 

Dissolve  a  silver  coin,  e.g.,  a  dime,  by  heat,  in  dilute 
nitric  acid.  There  is  copper  in  silver  coins.  What  two 
salts  then  are  in  the  nitric  acid  solution?  If  there 
seems  much  nitric  acid  left  it  should  be  mostly  evapo- 
rated off.  Insert  a  clean  strip  of  copper  and  set  aside 
for  some  time.  Explain  the  change.  Collect  the  silver 
deposited.  Throw  it  on  a  filter,  and  wash  thoroughly 
with  water  from  the  wash-bottle.  Why  wash  ?  Evap- 
orate the  filtrate  and  washings  to  dryness.  Examine 
the  substance  left.  What  is  it  ? 


yo  GOLD. 

METHOD  II.     BY  REDUCING  A  CHLORIDE. 

Dissolve  a  coin,  as  above,  in  nitric  acid.  Add  hydro- 
chloric acid  [or  a  solution  of  table  salt]  as  long  as  a 
precipitate  is  formed.  Explain  the  chemical  changes. 
Filter.  Wash  the  precipitate  thoroughly.  Why  ? 
Dry  the  precipitate.1  Remove  the  chloride  of  silver 
from  the  paper,  and  put  the  chloride  in  the  midst  of 
a  piece  of  combustion  tube.  Generate  hydrogen  gas. 
Take  every  precaution.  Fit  two  corks  to  the  combustion 
tube,  and  pass  hydrogen  gas  over  the  chloride  and  out 
through  an  exit  tube.  Light  the  hydrogen  by  the 
explosion  tube  and  in  no  other  way.  When  the  hydro- 
gen is  burning,  and  not  before,  heat  the  chloride  well. 
Note  the  effect  on  the  hydrogen  flame.  Explain. 
When  all  the  chloride  is  reduced,  examine  the  silver 
left.  What  is  reduction? 


Experiment  12. 

Gold.     [Aurum.] 

A.     The  Properties  of  Gold. 

Examine  a  small  piece  of  gold  [leaf  or  foil  will  do] 
and  note  its  chief  properties,  particularly  its  color, 
hardness,  and  malleability. 

B.     Action  of  Acids  on  Gold. 

Try  your  strongest  acids  on  gold.  Gold  is  called 
the  "  king  of  metals  "  because  of  its  resistance  to  the 
Action  of  acids. 

?  See  Appendix  M, 


CHLOKIDE   OF   GOLD.  9T 


C.  Chloride  of  Gold. 

By  treating  hydrochloric  acid  with  nitric  acid,  chlorine 
may  be  set  free.  Explain  this.  At  the  moment  chlorine 
is  set  free,  or,  as  it  is  called,  at  the  moment  of  its  birth 
[commonly  "  in  statu  nascendi "],  chlorine  has  unusual 
power  of  uniting  with  other  things.  Explain  this  great 
power  of  nascent  chlorine.  Nascent  chlorine  can,  with 
success,  attack  gold  and  produce  gold  chloride. 

Put  in  a  watch-glass  a  drop  or  two  of  hydrochloric 
acid  and  a  drop  of  nitric  acid.  Warm,  and  drop  in 
about  1  sq.  cm.  of  gold  foil.  Note  effect.  Carefully 
evaporate  the  solution  and  examine  the  gold  chloride 
formed.  The  mixture  of  hydrochloric  and  nitric  acids 
is  called  aqua  regia,  or  royal  water,  as  it  attacks  gold, 
the  king  of  metals.  Silver  and  gold  are  called  the 
noble  metals  because  they  do  not  tarnish  in  ordinary 
air. 

D.  Gold  Amalgam. 

Put  a  small  drop  of  mercury  on  a  watch-glass. 
Spread  over  it  a  piece  of  gold  leaf  as  large  as  a 
sq.  cm.  Note  effect.  Why  should  a  gold  ring  be 
kept  out  of  mercury? 

E.     Color  of  Gold. 

Examine  a  piece  of  gold  leaf,  or  foil,  as  it  lies  with 
the  light  reflected  from  it.  Hold  a  piece  of  gold  leaf 
up  to  the  light  and  note  the  color  as  the  light  is 
transmitted  through  it.  Best  lay  the  leaf  on  a  plate 
of  glass  for  convenience  in  handling. 


98  PLATINUM. 

Experiment  13. 

Platinum. 
A.     The  Properties  of  Platinum. 

Examine  a  small  bit  of  platinum  and  get  the  chief 
properties,  particularly  color  and  fusibility.  Why  is 
platinum  an  excellent  substance  from  which  to  make 
crucibles  ? 

B.     Action  of  Acids  on  Platinum. 

Try  your  strongest  acids  on  platinum.  Also  aqua 
regia.  Save  any  salts  formed. 

C.    Action  of  Other  Chemicals,  besides  Acids,  on  Platinum. 

Try  other  chemicals  [than  those  of  B],  e.g.,  alkalies, 
salts,  etc.  Why  is  platinum  an  excellent  substance  for 
chemical  utensils  ? 

1).     Action  of  Metals  with  Platinum. 

Heat,  in  a  clean  crucible,  a  bit  of  platinum  with  a  bit 
of  lead.  Note  the  formation  of  a  fusible  alloy.  Why 
should  not  metals  be  heated  in  platinum  dishes  ? 

E.     Platinum  Sponge. 

Put  about  2CC  of  a  solution  of  chloride  of  ammonium 
in  a  tt.  Render  acid  with  hydrogen  chloride  solution. 
Add,  drop  by  drop,  the  chloride  of  platinum  solution 
made  in  B.  Note  the  formation  of  a  yellow  precipitate. 
Collect  about  lcc  of  this  —  having  made  sure  that  the 


ALUMINUM.  99 

ammonium  chloride  is  in  excess,  and  not  the  platinic 
chloride.  Separate  the  precipitate,  by  decantation, 
from  its  liquor.  Dry  the  precipitate  a  little  by  very 
gentle  heat.  When  it  is  only  slightly  moist,  put  it 
in  a  bit  of  platinum  foil,  made  into  a  little  cup,  and 
heat  to  redness  in  a  small  Bunsen  flame  as  long  as 
fumes  are  given  off.  All  the  simple  substances,  except 
the  platinum,  will  go  off.  What  then  go  off?  Examine 
the  platinum  sponge  formed.  It  is  metallic.  Direct 
a  small  jet  of  house  gas  [better,  hydrogen]  against  a 
surface  of  freshly-made  platinum  sponge.  Note  effect. 


Experiment  14. 
Aluminum. 

A.     The  Properties  of  Aluminum. 

Examine  the  metal  —  ingot,  sheet,  or  wire  form  - 
and  note  the  chief  properties,  as  color,  lustre,  hardness, 
and,  approximately,  the  specific  gravity. 

B.     Oxidation  of  Aluminum. 
Try  to  oxidize  aluminum. 

C.     Action  of  Acids  on  Aluminum. 

Try  all  the  acids  you  can  —  diluted  and  strong  — 
hot  and  cold.     Results  in  a  table. 

1).     Sulphate  of  Aluminum. 
Prepare  the  sulphate  and  crystallize  it. 


100  ALUM. 


E.     Alum. 

Make,  in  a  tt,  a  saturated  solution  of  sulphate  of 
aluminum.  In  a  second  tt  make  a  saturated  solution 
of  sulphate  of  potassium.  Take  10CC  of  each  of  these 
solutions.  Mix.  Shake.  Evaporate  about  one  third 
the  water.  Let  crystallize.  Examine  the  crystals 
under  a  microscope,  comparing  them  with  the  original 
crystals  of  sulphate  of  aluminum  and  sulphate  of  potas- 
sium. Recrystallize  the  alum  from  hot  water.  Nurse l 
a  good  crystal.  Compare  the  solubility  of  the  alum 
with  that  of  the  original  sulphates.  What  is  an  alum  ? 

1  See  Appendix  N. 


PART   III. 


HISTOEY  AND  DEVELOPMENT 


LAWS  AND  THEORIES  OF  CHEMISTRY. 


PART   III. 
LAWS   AND    THEORIES    OF   CHEMISTRY. 


CHAPTER   I. 

INTRODUCTION. 

CHEMISTRY  may  be  defined  as  that  department  of 
human  knowledge  which  has  to  do  with  those  phe- 
nomena that  result  from  changes  of  substance. 

An  examination  of  the  many  changes  to  which 
matter  is  subject  shows  that  these  changes  fall  into 
two  groups  —  there  are  changes  in  which  the  compo- 
sition of  the  substance  is  not  altered,  and  others  in 
which  there  is  a  change  of  substance.  The  first  are 
called  physical  changes,  the  second  chemical.  As 
examples  of  physical  changes  may  be  given  :  the 
formation  of  the  solid,  ice,  from  the  liquid,  water  ; 
the  glowing  of  platinum  wire  when  the  electric  cur- 
rent is  passed  through  it ;  the  dissolving  of  sugar 
when  stirred  into  water.  In  no  one  of  these  cases 
is  it  thought  there  is  any  change  of  substance,  i.e., 
the  ice  is  oxide  of  hydrogen  just  as  much  as  is  the 
water,  the  platinum  is  still  platinum,  and  the  sugar 
remains  sugar.  But  when  the  electric  current  was 
passed  through  water  we  found  that  the  water  dis- 
appeared, and  two  gases  of  unlike  properties  were 


104  CHEMICAL   CHANGES. 

evolved ;  when  platinum  was  treated  with  aqua  regia, 
in  Ex.  13,  B,  Part  II,  a  chloride  not  at  all  like  the 
metal  platinum  resulted  ;  when  sugar  is  dropped  on 
a  hot  stove  a  black  charcoal  is  left,  while  water  vapor 
passes  off  into  the  air.  These  last  are  chemical 
changes  because  in  every  one  there  has  been  a  change 
of  substance. 

When  a  rod  of  iron  becomes  heated  and  glows  with 
a  red  color,  is  the  change  a  physical  one,  or  is  it 
chemical  ?  When  iron  becomes  magnetized,  and  is 
capable  of  attracting  to  itself  other  pieces  of  iron,  to 
which  class  does  the  change  belong?  When  iron 
burns  and  the  black  oxide  is  left,  when  it  is  acted 
on  by  moist  air  and  the  red  rust  is  left,  or  when  it  is 
acted  upon  by  sulphuric  acid  and  the  green  sulphate 
is  left,  what  are  the  changes,  chemical  or  physical  ? 
Give  the  reasons  for  your  answers.  When  glass  is 
softened  by  heat  is  the  change  chemical  or  physical  ? 
When  the  iron  filings  were  heated  in  contact  with 
air  was  the  blackening  of  their  surface  caused  by  a 
physical  or  a  chemical  change  ?  When  salt  stirred  into 
water  disappears  is  the  change  physical  or  chemical? 
Answer  this  last  question  after  doing  the  following 
experiment. 


Experiment  1. 
Two  Kinds  of  Changes. 

1.  Dissolve  about  one  gram  of  table  salt  in  about 
10CC  of  water.  Evaporate  the  water,  and  examine  the 
residue  as  to  color,  taste,  etc.  Note  that  it  is  the  same 


SOLUTION.  105 

salt  that  was  taken,  i.e.,  there  has  been  no  change  of  the 
substance,  therefore  the  solution  is  called  a  physical 
change. 

2.  Warm,  in  a  tt,  with  a  little  sulphuric  acid  and 
about  10CC  of  water,  some  iron  filings  till  solution  takes 
place.     Evaporate  the  liquid,  and  examine  the  residue. 
What  kind  of  a  change  has  taken  place  ?     How  do  you 
know  ?     Which  dissolved  —  the  iron,  or  the  sulphate 
of   iron    which    resulted   from    the    chemical  change  ? 
Would  it  be  right,  as  is  frequently  done,  to  call  this 
a  chemical  solution  of  the  iron? 

3.  Have  ready  a  porcelain  evaporating  dish  contain- 
ing 15-20CC  of  water.     Take  about  5g  of  dry  powdered 
carbonate  of  sodium  and  stir  this  into  the  water  till  a 
clear  solution  results.     Evaporate  to  dry  ness.     Examine 
the  residue.     Compare  it  with  carbonate  of  sodium  in 
color,  form,1  and  taste.     What  is  it  ? 

Next  put  15-20CC  of  hydrochloric  acid  solution  in  a 
porcelain  dish.  Add  about  5g  of  carbonate  of  sodium 
and  stir  till  a  clear  solution  results.  Evaporate  to 
dry  ness.  Examine  the  residue.  Compare  it  with  the 
original  carbonate  of  sodium  in  color,  form,1  and  taste. 
What  is  it  ?  What  kind  of  a  change  took  place  when 
water  alone  was  used?  When  hydrochloric  acid  was 
used  ?  What  went  into  the  solution  in  the  first  place  ? 
What  in  the  second  ?  How  do  you  distinguish  between 
a  simple  physical  solution  and  a  chemical  solution  ? 

The  loss  or  gain  of  water  sometimes  causes  a  change. 
Recall  the  change  that  followed  when,  in  Ex.  14, 

1  The  form  can  best  be  observed  under  a  microscope  of  medium 
power. 


106  HYDRATION. 

Part  I,  the  water  of  crystallization  was  driven  out 
by  heat  from  the  green  crystals  of  sulphate  of  iron  ; 
also  the  changes  when,  in  Ex.  27,  Part  I,  sal  soda 
effloresced,  and  when  [in  the  same  experiment]  sodium 
hydrate  deliquesced. 


Experiment  2. 
Changes  caused  by  Water  of  Crystallization. 

Put  a  small  lump  of  blue  crystallized  sulphate  of 
copper  in  a  porcelain  crucible,  and  warm  gently  till 
the  water  of  crystallization  has  gone.  Note  change 
in  color.  Add  a  little  water.  Again  note  change  in 
color. 


Experiment  3. 

Change  caused  by  the  Action  of  Sulphuric  Acid  on 

Water. 

Put  about  20CC  of  cold  water  in  a  tt.  Add,  cau- 
tiously, about  5CC  of  sulphuric  acid.  Stir  with  a  glass 
rod.  Note  the  change  in  temperature. 

Note.  These  changes,  caused  by  the  removal  or  addi- 
tion of  water,  seem  to  lie  in  the  borderland  between 
the  true  physical  changes  and  the  true  chemical  ones. 
Some  chemists  think  that  simple  solution  [e.g.,  when 
salt  disappears  by  dissolving  in  water,  or  when  sul- 
phuric acid  dissolves  in  water]  is  always  accompanied 
by  a  reaction  of  the  substance  with  the  solvent. 


ANALYTICAL  CHEMISTRY.  107 


Analyses.    Syntheses.    Metatheses. 

Changes  of  substance,  that  is,  chemical  changes,  may 
be  divided  into  three  classes,  analyses,  syntheses,  and 
metatheses. 


Changes  of  Substance  by  Analyses. 

ANALYTICAL  CHEMISTRY. 

The  word  analysis  is  derived  from  the  Greek,  and 
means  an  unloosing.  It  is  applied  in  chemistry  to 
unloosing  the  bonds  which  bind  together  the  con- 
stituents of  a  compound.  Those  changes  in  which 
compound  substances  are  separated  into  simpler  con- 
stituents are  called  analytical. 

Analysis  may  be  either  proximate  or  ultimate.  A 
proximate  analysis  is  one  in  which  a  compound  is 
separated  into  simple  constituents,  but  not  necessarily 
into  the  simplest;  e.g.,  when  we  found,  by  heating, 
that  marble  was  separated  into  two  oxides  —  oxide  of 
carbon  and  oxide  of  calcium  —  we  made  a  proximate 
analysis.  Both  constituents,  however,  were  capable  of 
further  separation.  An  ultimate  analysis  is  one  in 
which  the  simplest  constituents  of  a  compound  are 
determined;  e.g.,  when,  by  heating  red  oxide  of  mer- 
cury, we  found  that  it  was  separated  into  two  sub- 
stances —  mercury  and  oxygen  —  neither  of  which  has 
been  separated,  we  made  an  ultimate  analysis. 

Note  that  already  we  have  made  analytical  changes 
in  several  cases.  Review  your  laboratory  work,  and 
now  note  the  analyses  made  of 


108  SYNTHETICAL   CHEMISTRY. 

Red  oxide  of  mercury,     v- 

Water  [hydrogen  oxide],  ^ 

Sulphuretted  hydrogen  [hydrogen  sulphide],  p 

Carbonic  dioxide,  *- 

Hydrochloric  acid,  -" 

Marble.   £ 
f 

State  in  every  case  into  what  factors  each  substance 
was  analyzed. 

Changes  of  Substance  by  Syntheses. 

SYNTHETICAL  CHEMISTRY. 

The  word  synthesis  is  derived  from  the  Greek,  and 
means  putting  together.  It  is  applied  in  chemistry  to 
the  formation  of  compounds.  Synthetical  chemistry  is- 
the  opposite  of  analytical.  We  have  already  made 
syntheses  many  times.  Refer  to  the  proper  experi- 
ments, and  explain  the  syntheses  of 

Iron  oxide,  Sulphuretted  hydrogen, 

Water,  Slaked  lime, 

Sulphurous  acid,  Hydrochloric  acid, 

Sulphuric  acid,  Table  salt. 

State  the  factors  in  each  case. 


Experiment  4. 
Synthesis  of  Chloride  of  Ammonium. 

Make  a  synthesis  of  chloride  of  ammonium  from 
ammonia  gas  and  hydrochloric  acid  gas.  Put  a  little 
aqua  ammonia  in  a  tt,  and  a  little  hydrochloric  acid 


METATHETICAL   CHEMISTRY.  109 

solution  in  a  second  tt.  Bring  the  mouths  of  the 
two  tubes  near  each  other.  The  gases  will  join  in 
the  air,  and  white  fumes  of  the  chloride  of  ammonium 
appear.  If  the  action  is  not  rapid  enough,  heat  each 
tt  to  drive  the  gases  from  their  solutions. 

Changes  of  Substance  by  Metatheses. 

METATHETICAL  CHEMISTRY. 

The  word  metathesis  is  derived  from  the  Greek,  and 
means  an  exchanging.  It  is  applied  in  chemistry  to 
those  changes  in  which  two  or  more  substances  change 
places;  e.g.,  when  hydrogen  is  made  by  the  action  of 
zinc  on  sulphuric  acid,  the  change  is  metathetical,  for 
'the  zinc  takes  the  place  of  the  hydrogen,  and  the 
hydrogen  is  left  in  a  free  condition  as  was  the  zinc 
at  first.  We  have  already  made  a  great  many  metath- 
eses.  Cite  references,  and  explain  the  metathetical 
changes  when  you  made 

Hydrogen  from  sulphuric  acid, 

Hydrogen  from  water  by  means  of  hot  iron, 

Zinc  sulphate  from  zinc  oxide  and  sulphuric  acid, 

Combustible  oxide  of  carbon, 

Sulphuretted  hydrogen  from  sulphide  of  iron  and  an  acid, 

Sulphate  of  magnesium, 

Marble  powder,  • 

Sulphate  of  sodium, 

Hydrochloric  acid  from  table  salt, 

Carbonate  of  potassium  from  potassium  and  dioxide  of  carbon, 

Nitric  acid. 


110  METATHESES. 

Experiment  5. 
Metatheses. 

1.  Dissolve  about  5g  of  nitrate  of  lead  in  about  100CC 
of  water.     Put  the  solution  in  a  beaker.     Insert  a  small 
strip  of  clean  zinc.     Note  the  changing  places  by  the 
zinc  and  the  lead  —  the  lead  lets  go  its  hold  of  the 
nitrogen  and  oxygen  part  of  the  nitrate  and  appears 
as  metallic  lead,  while  the  zinc  joins  that  which  the 
lead  has  left. 

2.  In  a  tt  dissolve  about  one  tenth  of  a  gram  of 
silver  nitrate  in  about  5CC  of  water.      In  a  second  tt 
dissolve  about  one  third  as  much  table  salt  in  about 
5CC  of  water.     Pour,  drop  by  drop,  one  solution  into, 
the  other.     Here  there  is  an  interchange  —  the  silver 
leaving  its  nitrogen  and  oxygen  to  join  the  chlorine 
which  leaves  its  sodium,  while  the  sodium  joins  the 
nitrogen  and  oxygen  left  by  the  silver.     The  chloride 
of  silver,  not  being  soluble  in  water,  appears  as  a  heavy 
precipitate. 

3.  Dissolve  about  lg   of  potassic  sulphocyanate  in 
about  200CC  of  water  in  a  beaker.      Potassic  sulpho- 
cyanate,  on  analysis,   is  found  to  contain  potassium, 
sulphur,  carbon,  and  nitrogen  —  the  potassium  having 
taken  the  place  of  the  hydrogen  in  an  acid  consisting 
of  hydrogen  -f  sulphur  +  carbon  -}-  nitrogen.      Into 
this  solution   drop   a   single   drop   of   ferric  chloride. 
Look  for  the  metathesis  as  the  chloride  of  iron  falls 
through   the   solution.      What  simple   substances  are 
there    in    ferric    chloride?      Explain    the    metathesis 
here. 


THE   EARLIEST    PERIOD.  Ill 


CHAPTER    II. 
THE   EARLIEST    PERIOD. 

examination  of  the  records  of  very  ancient 
nations,  as  the  Chinese,  Jews,  Egyptians,  and  Phoe- 
nicians, shows  that  these  people  possessed  some  knowl- 
edge of  chemical  processes.  The  Chinese  early  learned 
the  arts  of  glass  and  porcelain  making.  The  Phoe- 
nicians are  noted  for  their  skill  in  dyeing.  The  Jews, 
as  shown  by  the  Old  Testament,  were  acquainted  with 
certainly  four,  and  probably  six,  metals,  some  of  which 
could  be  obtained  only  from  ores,  by  chemical  means. 
And  the  Egyptians  are  famous  not  only  for  their 
knowledge  of  a  large  number  of  chemical  processes, 
but  for  the  skill  with  which  they  applied  these  in  their 
arts.  Independently  of  the  Chinese,  the  Egyptians 
discovered  a  method  for  making  glass.  It  is  probable 
that  this  discovery  was  accidental,  soda  having  been 
added  to  sand  as  a  flux  to  aid  in  separating  gold  from 
the  sand.  It  was  chiefly  from  the  Phoenicians  and 
Egyptians  that  the  Greeks,  and  later,  the  Romans, 
obtained  considerable  knowledge  of  chemical  pro- 
cesses. 

But  all  the  chemical  knowledge  of  these  ancient 
nations  was  disjointed,  unclassified,  and  never  do  we 
find  an  attempt  at  a  scientific  explanation  of  chemical 
phenomena.  It  is  strange  that  a  critical  examination 
of  chemical  changes  could  have  escaped  the  keen 
minds  of  the  Greeks.  Their  whole  attention  seems 
to  have  been  given  to  the  deductive  method  of 


112  THE   EABLIEST   PERIOD. 

reasoning.  Seldom  did  they  study  Nature  inductively,1 
and  never  do  they  seem  to  have  tested  their  deduc- 
tions by  experiments.  Though  the  Ancients  never 
deliberately  planned  experiments  to  give  an  insight 
into  the  constitution  of  bodies,  they  made  numerous 
speculations  as  to  the  nature  of  the  world,  and  the 
matter  of  which  it  consists.  The  most  celebrated 
of  these  is  Aristotle's  theory  of  the  elements.  By 
elements  are  here  meant  the  foundation  substances 
of  which  all  the  world  is  made. 

Aristotle  assumed  that  there  were  four  of  these 
elements  —  earth,  water,  air,  and  fire.  But  to  Aris- 
totle these  words  did  not  convey  the  same  meaning 
that  they  do  to  us.  To  him  they  represented  different 
properties  that  matter  itself  possesses :  earth  stood  for 
that  which  is  cold  and  dry;  water  for  the  cold  and 
wet;  air,  hot  and  wet;  fire,  hot  and  dry.  But  these 
four  were  not  entirely  sufficient  to  Aristotle  for  explain- 
ing all  phenomena.  Hence  he  added  -a  fifth,2  called 

1  The  distinction  between  the  deductive  and  inductive  methods  of 
reasoning  should  be  well  fixed  in  mind.      The  inductive  method  is 
preeminently  the  method  by  which  the  far-reaching  developments  in 
all  branches  of  natural  science  during  the  last  centuries  have  been 
attained.     The  facts  have  first  been  observed,  collected,  and  arranged. 
Then  from  the  special  cases  general  principles  have  been  discovered. 
The  deductive  method  is  the  method  of  speculative  philosophy.     It  is 
the  method  employed  so  largely  by  the  Greek  and  most  other  philoso- 
phers.     From  general  principles  deductions  are  made  to  fit  special 
cases. 

2  This  fifth  element  of  Aristotle  became  later  the  quinta  essentia 
[whence  our  word  quintessence]  of  the  Alchemists,  among  whom  it 
caused  much  trouble.      They  made  many  vain  endeavors  to  obtain 
this,  not  understanding  that  Aristotle  considered  it  of  the  nature  ol 
spirit  and  not  matter,  and  therefore  intangible. 


THE   EARLIEST   PEKIOD.  113 

aether.  This  last  was  all-pervading  and  of  a  spiritual 
nature.  Although  this  theory  of  the  elements  is  called 
the  Aristotelian  it  is  said  to  have  originated  with 
Empedocles,  who  flourished  about  a  hundred  years 
before  Aristotle,1  and  it  is  possible  that  Empedocles 
himself  obtained  it  from  some  earlier  source,  as  it  is 
claimed  that  ancient  writings  in  India  declare  the 
world  is  made  of  five  elements,  earth,  water,  air,  fire, 
and  aether;  while  Buddha  considered  it  made  of  these 
five  together  with  a  sixth  —  consciousness. 

For  Review?  Of  what  nature  was  the  chemical 
knowledge  possessed  by  the  ancient  nations  ?  Mention 
a  chemical  process  known  to  the  Chinese,  to  the  Jews, 
to  the  Phoenicians,  to  the  Egyptians.  Where  did  the 
Greeks  and  Romans  get  their  knowledge  of  chemical 
processes  ?  How  did  the  Ancients'  treatment  of  chem- 
ical phenomena  differ  from  our  own  ?  What  is  meant 
by  the  deductive  method?  What  by  the  inductive? 
Give  an  illustration  of  the  use  of  the  inductive  method. 
[This  illustration  may  well  be  taken  from  "  A  Chemical 
Investigation,"  Part  I,  of  this  book.] 

1  Aristotle  lived  384-322  B.C. 

2  To  the  Student.     After  you  have  read  each  section  of  Part  III  you 
should  at  once  try  to  formulate  answers  to  the  questions  asked.     If 
you  cannot  make  satisfactory  answers  to  all,  re-read  the  whole  section, 
looking  particularly  for  answers  to  the  questions  that  have  troubled 
you.     Again  formulate  answers  to  all  the  questions,  and,  if  any  are 
still  unanswered,  search  for  the  proper  answers  without  re-reading  the 
whole  section. 


114  THE   PERIOD   OF   ALCHEMY. 

CHAPTER    III. 
THE   PERIOD   OF   ALCHEMY. 

ACCORDING  to  Aristotle's  theory,  water  is  cold  and 
wet,  while  air  is  hot  and  wet.  Each,  then,  has  a 
common  property  —  wetness.  It  was  thought  that 
when  the  substance  water  is  heated  and  boils  away 
it  becomes  air.  This  was  considered  a  transmutation, 
that  is,  a  changing  of  one  substance  into  another. 
During  the  years  that  immediately  preceded  the  Chris- 
tian era,  and  during  the  first  years  of  this  era,  many 
men  came  to  think  that  if  a  change  of  the  nature  just 
indicated  was  possible,  it  must  be  possible  also  to 
change  a  base  metal  into  a  noble,  e.g.,  to  transmute 
lead  into  gold.  It  was  at  this  time,  it  may  be  said, 
that  chemistry  began  to  have  a  being.  Not  that 
chemistry  as  a  science  began  to  exist  so  early,  but 
chemistry  as  a  distinct  department  of  knowledge.  Up 
to  this  time,  as  has  been  shown  in  Chapter  II,  many 
nations  possessed  a  knowledge  of  a  number  of  chemical 
processes,  but  it  does  not  appear  that  any  attempt  had 
been  made  to  collect  a  knowledge  of  these  processes 
into  a  distinct  class,  or  to  direct  a  number  of  them  to 
the  attainment  of  a  given  end.  But  when  the  atten- 
tion of  men  became  centered  on  the  problem  of  the 
transmutation  of  metals,  then  it  was  that  chemical 
processes  began  to  be  grouped  together  and  used  for 
the  solution  of  the  problem.  Even  then,  however, 
no  attempt  was  made  to  group  the  processes  in  any 
natural  series  or  to  explain  the  phenomena.  As  late 


THE   EGYPTIAN   AKT.  115 

as  the  eleventh  century,  chemistry  has  been  defined  [in 
an  encyclopedia  by  Suidas]  as  "  the  artificial  preparation 
of  silver  and  gold." 

The  word  chemeia,  from  which  comes  our  word  chem- 
istry, has  been  traced  back  to  the  fourth  century,  but 
was  probably  used  even  before  that.  Its  derivation  is 
uncertain.  There  is  a  word  chemi,  an  ancient  name  for 
Egypt.  This  word  also  meant  dark,  and  may  have  been 
applied  to  Egypt  on  account  of  the  dark  color  of  its  soil. 
The  word  was  also  applied  to  the  dark  or  mysterious 
portion  of  the  eye,  and  also,  it  is  said,  to  a  black  prepa- 
ration used  in  alchemy.  Hence  it  is  somewhat  doubtful 
whether  chemeia  meant  the  Egyptian  art,  the  black  or 
mysterious  art,  or  the  art  which  made  use  of  this  prepa- 
ration. The  term  alchemy  comes  from  the  Greek  word 
chemeia,  and  the  Arabic  article  al  used  as  a  prefix. 

The  period  of  alchemy  began  with  the  first  attempt 
at  the  transmutation  of  base  metals  into  silver  and 
gold,  and  extended  into  the  sixteenth  century,  when 
chemistry  gradually  passed  into  its  medical  period. 
No  exact  date  can  be  set  for  the  origin  of  alchemy. 
In  searching  for  its  rise,  tradition  carries  us  far  back 
among  the  myths  of  the  past,  but  historical  proof  of 
the  practice  of  alchemy  is  wanting  before  the  fourth 
century.  It  was  in  Egypt,  and  toward  the  close  of 
the  fourth  century  and  during  the  first  years  of  the 
fifth,  that  alchemy  first  attained  distinction.  In  the 
seventh  century,  the  Arabs  overran  Egypt  and  absorbed 
the  chemical  knowledge  together  with  many  other 
things  possessed  by  the  Egyptians.  Early  in  the  eighth 
century  the  Arabs  advanced  and  captured  Spain.  Here 


116          THE  PERIOD  OF  ALCHEMY. 

they  founded  universities,  and  for  years  fostered  learn- 
ing and  the  arts.  To  the  Arabian  universities  in  Spain 
there  came  many  students  from  the  western  nations, 
particularly  from  France,  Italy,  and  Germany.  Here 
alchemy  was  studied,  and  these  students,  on  their 
return,  spread  alchemistic  ideas  among  many  nations. 
It  may  be  said  that  alchemy  reached  its  height  in  the 
thirteenth  century,  and,  although  in  the  sixteenth  it 
began  to  be  supplanted  by  medical  chemistry,  it  did 
not  entirely  die  out  till  many  years  later.  In  the 
seventeenth  century,  Van  Helmont  says  that  he  changed 
mercury  into  gold,  claiming  to  have  a  substance  one 
part  of  which  could  transmute  two  thousand  parts  of 
mercury.  In  the  eighteenth  century,  too,  pieces  of 
metal  [usually  bronze  covered  with  gilt]  were  often 
shown  as  proofs  of  alchemistic  changes,  and  even  as 
late  as  the  present  century1  it  has  been  claimed  that 
metals  have  really  been  transmuted.  In  order  to  see 
on  what  kind  of  observations  the  alchemists  based  their 
hope  of  transforming  metals,  let  us  for  the  time  being 
put  aside  all  the  knowledge  of  chemical  changes  which 
we  have  gained  from  our  work  in  the  laboratory,  and 
try  the  following  experiments  which  the  old  alchemists 
used  to  perform. 


Experiment  6. 
A  So-Called  Transmutation. 

In  a  small  beaker  put  about  50CC  of  strong  copper 
sulphate  solution.      In  this  immerse  a  piece  of  sheet 
1  See  Schmieder's  History  of  Alchemy,  1832. 


ALCHEMISTIC   EXPERIMENTS.  117 

iron.1  When  a  deposit  has  formed  on  the  iron,  remove 
this  deposit,  press  it  into  a  ball,  lay  it  on  the  desk  and 
rub  it  with  some  hard  instrument  in  order  to  polish  it. 
Note  that  it  is  copper.  To  the  alchemists  this  seemed 
a  change  of  iron  into  copper.  Copper  sulphate  solu- 
tion was  obtained,  as  it  may  be  to-day,  from  the  pools 
that  form  in  certain  mines. 


Experiment  7. 
Death  of  a  Metal. 

Heat  in  a  small  Hessian  crucible,  over  a  blast-lamp, 
a  small  piece  of  lead.  Stir  well,  to  give  good  air 
contact,  till  there  is  left  only  a  dirty  powder.  Tp 
the  alchemists  the  metal  had  been  destroyed,  and  the 
ashes  left  were  the  remains  from  its  death. 


Experiment  8. 
Kesurrection  of  a  Metal. 

In  a  small  Hessian  crucible  heat  about  a  gram  of 
oxide  of  lead,  and  add  several  grains  of  wheat.2  Stir 
the  wheat,  as  it  chars,  into  the  oxide.  Continue  heat- 
ing and  adding  wheat  till  globules  of  molten  lead 
appear.  To  the  alchemists  this  was  the  resurrection 
of  the  metal.  How  do  you  explain  the  transformation? 

1  Nails,  stout  wire,  or  other  forms  of  iron  will  do  nearly  as  well. 

2  It  is  best  first  to  put  the  wheat  in  a  covered  crucible,  or  other  dish, 
and  heat  before  use.     Otherwise  the  grains  may  "pop"  and  cause 
annoyance. 


118  THE  PERIOD  OF  ALCHEMY. 

Although  the  transmutation  of  metals  was  the  most 
prominent  feature  of  alchemy,  there  early  crept  in  a 
second  pursuit  which  soon  claimed  a  large  share  of 
attention.  This  latter  was  a  search  for  the  Philoso- 
pher's Stone,  a  substance  of  miraculous  powers.  Not 
only  was  it  to  be  the  means  by  which  the  transmuta- 
tions themselves  were  to  be  effected,  but  it  was  to  be 
a  cureall  for  disease,  and  a  bestower  of  long  life  and 
perpetual  youth  upon  its  possessor.  Many  are  the 
claims  for  the  discovery  and  virtues  of  this  stone  — 
some  of  them  most  preposterous.  Thus,  Roger  Bacon 
claims  that  it  could  transform  more  than  a  million  times 
its  weight  of  a  base  metal  into  gold.  Many  alchemists 
who  claimed  to  possess  it  declared  that  they  had  pro- 
longed their  lives  three  hundred,  four  hundred,  and 
even  more  years.  Even  the  production  of  living  beings 
by  its  means  was  believed  possible. 

It  is  interesting  to  note  that  in  the  period  of  alchemy 
we  find  theories  proposed  for  the  composition  of  sub- 
stances. Geber,1  the  most  famous  of  the  Arabian 
alchemists,  held  that  there  were  two  elementary  sub- 
stances, mercury  and  sulphur.  As  Aristotle's  elements 
do  not  correspond  with  our  substances  of  the  same 
names,  so  Geber's  mercury  and  sulphur  must  not  be 
mistaken  for  the  substances  to  which  we  give  these 
names.  Mercury  to  him  was  that  which  produced 
lustre,  malleability,  and  other  metallic  properties,  while 
sulphur  was  that  which  caused  combustibility.  Geber 
believed  the  metals  were  compounds,  that  the  noble 
metals  were  very  rich  in  mercury  while  the  base  ones 

1  He  was  a  physician  who  flourished  in  the  eighth  century. 


ALCHEMISTIC   THEORIES.  119 

contained  an  excess  of  sulphur.  By  this  theory  it  did 
not  seem  unreasonable  to  suppose  that  sulphur  might 
be  withdrawn  from  a  base  metal,  and  in  this  way  trans- 
formation accomplished.  Valentine,  the  most  eminent 
man  of  the  last  years  of  the  period  of  alchemy,  added 
a  third  element,  salt,  to  Geber's  mercury  and  sulphur. 
Salt  to  .him,  'however,  was  not  what  we  mean  by  salt. 
It  was  the  principle  which  enabled  a  body  to  resist  fire 
and  maintain  a  solid  condition.  Valentine  proposed 
the  use  of  chemical  preparations  in  medicine,  and  a 
little  later  chemistry  and  medicine  became  so  much 
allied  that  it  is  customary  to  speak  of  the  following 
years  as  the  iatro,  or  medical,  period  of  chemistry. 

For  Review.  When  was  the  period  of  alchemy  ?  Give 
the  derivation  of  the  words  chemistry  and  alchemy. 
What  was  the  original  pursuit  of  the  alchemists  ?  What 
a  second  -pursuit  ?  Where  did  alchemy  probably  have 
its  birth  ?  What  part  did  the  Arabs  play  in  the  devel- 
opment of  alchemy  ?  In  what  way  did  alchemy  spread 
over  the  western  world?  Mention  two  famous  alche- 
mists. What  was  Geber's  theory  of  the  composition  of 
substances?  What  did  Valentine  add  to  Geber's  ele- 
ments ?  What  important  step  did  Valentine  propose  ? 


120  THE   MEDICAL   PERIOD. 

CHAPTER   IV. 

THE   MEDICAL  PERIOD. 

ALTHOUGH  chemical  preparations  had  now  and  then 
during  the  period  of  alchemy  been  used  in  medicine, 
it  was  Paracelsus1  who,  during  the  first  half  of  the 
sixteenth  century,  united  chemistry  and  medicine. 
He  boldly  maintained  that  the  "object  of  chemistry 
is  not  to  make  gold,  but  to  prepare  medicines."  He 
considered  the  human  body  made  up  of  chemical  sub- 
stances, and  believed  that  changes  in  these  substances 
caused  diseases  which  could  be  cured  by  the  adminis- 
tration of  chemical  preparations.  Following  the  lead 
of  Paracelsus,  the  chief  aim  of  chemists  for  more  than 
a  century  was  the  establishment  of  medicine  upon  a 
chemical  basis.  The  result  of  this  new  development 
in  chemistry  was  of  great  good  to  both  chemistry  and 
medicine.  On  the  one  hand,  the  properties  of  chem- 
icals were  carefully  observed,  methods  for  preparation 
elaborated,  and  many  new  substances  found  ;  while, 
on  the  other  hand,  corrosive  sublimate,  sugar  of  lead, 
compounds  of  antimony,  and  many  other  substances 
previously  considered  too  poisonous  to  use  in  medicine, 
became  valuable  agents  for  the  physician.  It  was  during 
this  period  that  the  German,  Libavius,  in  1595,  published 
the  first  chemical  text-book  of  note  —  his  Alchymia. 

Perhaps  the  most  eminent  chemist  of  this  period 
was  Van  Helmont,  of  Brussels.2  He  did  not  accept 

1  Paracelsus  lived  1493-1541.      He  was  born  in  Switzerland,  but 
traveled  and  worked  in  many  lands. 

2  Van  Helmont  lived  1577-1644. 


VAN   HELMONT.  121 

Aristotle's  theory  of  the  elements,  nor  was  he  satisfied 
with  that  of  Geber  or  of  Valentine.  He  denied  that 
fire  had  any  material  existence,  and  announced  that 
when  a  metal  is  treated  with  an  acid  and  disappears 
it  is  not  destroyed,  proving,  as  he  did  by  experiment, 
that  a  substance  continues  to  exist  in  its  compounds. 
Of  equal  importance  with  his  other  researches  are  his 
observations  on  gases.1  Up  to  this  time  no  distinction 
had  been  made  between  the  various  gases,  such  as 
hydrogen,  carbonic  dioxide,  sulphurous  oxide,  etc.,  all 
being  considered  air.  Van  Helmont  not  only  made  a 
distinction  between  gases  and  vapors  —  calling  aeriform 
substances  which,  when  cooled,  became  liquids,  vapors  ; 
and  those  which  did  not,  gases  —  but  also  noted  the 
properties  of  a  number  of  aeriform  substances,  and  dis- 
tinguished one  from  another.  He  studied  particularly 
carbonic  dioxide,  which  he  called  gas  sylvestre.  This 
gas  he  found  could  be  obtained  when  coal  is  burned, 
when  beer  ferments,  by  treating  limestone  or  potash 
with  acids,  from  mineral  waters,  and  in  certain  caves. 
That  Van  Helmont  did  much  to  promote  the  union  of 
chemistry  and  medicine  is  shown  by  the  experiments 
that  he  carried  on  with  the  juices  and  secretions  of  the 
animal  body,  als*o  by  the  explanations  he  gave  for  the 
changes  which  take  place  within  the  body.  He  believed 
the  acid  of  the  gastric  juice  is  the  agent  which  causes 
digestion,  but  that  if  this  juice  exists  in  too  large  a 
quantity  sickness  results.  To  cure  this  kind  of  sick- 
ness he  used  as  medicine  alkaline  preparations,  while, 
to  cure  sickness  caused  by  a  lack  of  gastric  juice,  he 

1  It  was  Van  Helmont  who  invented  the  word  gas. 


122  THE   MEDICAL  PERIOD. 

administered  acid  substances.  That  Van  Helmont, 
though  preeminently  a  medical  chemist,  still  held 
alchemistic  beliefs  is  shown  by  an  elaborate  descrip- 
tion he  has  left  of  a  method  for  changing  mercury  into 
gold  and  silver.  And  it  may  also  be  said  that  his  work 
on  gases  should  give  him  a  place  in  a  period  which  is 
usually  put  a  little  later  —  the  pneumatic  period. 

During  these  years  of  medical  chemistry  there  lived 
three  men  who,  though  they  did  but  little  themselves 
toward  bringing  about  a  union  between  medicine  and 
chemistry,  yet  deserve  to  be  remembered  for  their 
work  in  practical  chemistry  —  Agricola,  a  German 
metallurgist,  Palissy,  a  French  potter,  and  Glauber, 
a  Bavarian  chemist. 

Agricola  was  a  physician,  but  while  he  practiced 
medicine  he  found  time  to  study  mineralogy  and  metal- 
lurgy in  the  mines  and  smelting  works  of  Saxony,  many 
of  whose  technical  products  he  has  described  in  a  book 
he  wrote. 

Palissy  devoted  himself  to  improving  the  art  of  mak- 
ing pottery.  He  cared  little  for  speculations,  and  did 
not  believe  in  the  theories  of  alchemists  nor  in  those  of 
Paracelsus  himself.  He  based  his  work  upon  experi- 
ments, and  although  at  first  he  met  many  disappoint- 
ments and  failures  he  finally  carried  his  art  to  a  high 
degree  of  perfection.  Especially  well  did  he  succeed 
in  making  enamels  and  in  enameling  earthen  ware,  par- 
ticularly that  ware  called  Faience.  The  records1  he 
has  left  are  characterized  by  clearness  and  simplicity. 

1  E.g.,  L'Art  de  Terre,  in  which  he  speaks  of  clays,  firings,  etc., 
shows  how  much  superior  is  experiment  to  theory  alone,  and  gives  a 
most  entertaining  account  of  his  early  struggles  and  mistakes. 


GLATTBEK.  123 

Glauber,1  who  has  been  called  the  Paracelsus  of  the 
seventeenth  century,  really  devoted  much  less  attention 
to  medical  •  chemistry  than  to  applied  chemistry.  He 
enriched  pharmaceutical  chemistry  with  many  prepara- 
tions. It  is  believed  that  he  first  obtained  hydrochloric 
acid  by  treating  table  salt  with  sulphuric  acid,  and  first 
obtained  nitric  acid  by  treating  nitre  with  sulphuric 
acid.  It  was  in  the  residue  from  making  hydrochloric 
acid  that  he  found  sulphate  of  sodium,  which  was  called 
sal  mirabile  Grlauberi,  and  to  this  day  bears  the  name  of 
Glauber's  salt.  Glauber  was  also  a  writer  on  economic 
subjects,  frequently  urging  Germany  to  make  use  of  its 
own  raw  materials  and  not  sell  so  much  of  these  to  other 
countries  only  to  buy  them  back  when  manufactured 
into  various  finished  products. 

In  the  course  of  this  medical  period  we  see  here  and 
there  a  use  made  of  the  inductive  method.  Experi- 
menting itself  was  already  largely  employed,  but  seldom 
were  theories  founded  on  the  results  of  the  experiments. 
Paracelsus  himself  spent  many  of  his  early  years  in 
travel,  claiming  that  the  true  way  for  a  physician  to 
gain  knowledge  of  real  value  was  not  to  read  books 
and  argue  over  the  precepts  of  the  Ancients,  but  to 
examine  cases  found  in  his  own  day  and  discuss  these.2 

1  Glauber  lived  1604-1668. 

2  It  is  sad  to  note  that  this  sensible  method  gained  for  him  nothing 
but  contempt  and  ridicule  from  his  fellow  physicians  who  clung  most 
tenaciously  to  the  "Authority  of  the  Ancients."     At  one  time  Para- 
celsus was  town  physician  at  Basel  and  here  talked  so  plainly  against 
the  impositions  practiced  by  the  pharmacists  that  the  latter  found 
means  for  having  him  driven  from  the  city,  and  it  is  even  said  that 
at  a  later  period  these  same  enemies  caused  his  death  by  throwing 
him  over  a  precipice. 


124  THE   MEDICAL   PERIOD. 

Palissy,  we  find,  made  experiment  the  sole  basis  for 
his  work  in  pottery;  while  Van  Helmont  based  many 
of  his  assumptions  on  experiment,  unfortunately,  how- 
ever, not  interpreting  his  experiments  correctly,  as,  for 
instance,  when  he  assumed  that  water  was  the  basis  of 
all  organic  substances  because  water  appeared  whenever 
he  burned  these  ;  and,  again,  when  he  assumed  that 
only  water  was  necessary  for  the  growth  of  some  plants, 
because,  as  it  seemed  to  him,  he  had  been  able  to  make 
certain  plants  grow  on  the  surface  of  pure  water. 

For  Review.  Who  united  chemistry  and  medicine  ? 
When  ?  What  advantage  came  to  chemistry  from  this 
union  ?  What  to  medicine  ?  When  was  the  first  text- 
book on  chemistry  published?  What  did  Van  Hel- 
mont reject  ?  What  deny  ?  What  prove  ?  What  did 
he  observe  in  regard  to  gases  ?  Who  invented  the  word 
gas?  For  what  is  Agricola  noted?  For  what  Palissy? 
For  what  Glauber?  What  proof  have  we  that  the 
inductive  method  was  used  as  early  as  the  medical 
period  ? 


ROBERT  BOYLE.  125 

CHAPTER  V. 

PERIOD  OF  ROBERT  BOYLE. 

To  modest,  unpretending  Robert  Boyle,  chemistry  is 
so  much  indebted  that  we  are  justified  in  designating 
the  active  years  of  his  life  as  a  distinct  period  in  chem- 
ical history.  He  was  born  in  Ireland  in  1627,  but 
spent  most  of  his  life  in  England  where  he  died  at 
London  in  1691.  It  was  Boyle  who  first  saw  clearly 
that  the  inductive  method  is  the  only  safe  method  to 
follow  in  the  pursuit  of  knowledge.  He  it  was  who 
first  gave  a  proper  definition  for  the  term  element. 
And  to  Boyle  is  due  the  establishment  of  chemistry 
as  a  true  science.  But  these  three  important  results 
are  by  no  means  all  that  came  from  his  labors.  The 
discoveries  of  Boyle  were  of  particular  value  in  applied 
chemistry,  e.g.,  his  preparation  of  ruby  glass,  his  dis- 
covery of  phosphorus,1  phosphoric  acid,  etc. 

Boyle  also  devoted  his  attention  to  the  study  of 
gases,  as  is  shown  in  his  work  on  "  The  Spring  of  the 
Air"  and  in  other  publications.  His  keen  observation 
led  him  to  the  discovery  of  the  law  [in  regard  to  the 
effect  of  pressure  on  a  gas]  which  bears  his  name. 

1  Phosphorus  had  already  been  discovered  by  Brand  of  Hamburg, 
but  its  preparation  was  kept  a  secret  and  Boyle  had  to  rediscover  it. 


126          PERIOD  OF  ROBERT  BOYLE. 

Experiment  9. 

The  Law  of  Boyle.1 

Take  a  piece  of  glass  tube  8-10mm  bore,  of  uniform 
caliber,  about  1.5  meter  long,  closed  at  one  end  and 
bent  to  form  two  parallel  arms,  one  of  which  is  at  least 
three  times  as  long  as  the  other.  The  longer  arm  must 
have  the  open  end  of  the  tube.  Have  ready  about  500g 
of  mercury  that  is  clean  and  dry. 

Note.  Dirty  or  wet  mercury  will  not  give  a  good 
result,  and  will  render  the  tube  unfit  for  a  second 
determination.2  The  closest  attention  to  details  is 
necessary  in  this  experiment  if  a  satisfactory  result 
is  looked  for. 

Pour  a  little  mercury  into  the  tube  to  "seal  the 
bend."  Shake  the  mercury  around  till  it  stands  as 
high  in  one  arm  as  in  the  other,  when  the  two  arms 
are  upright,  thus  making  sure  that  the  confined  air 
is  not  under  any  abnormal  pressure  from  an  excess 
of  mercury  in  the  long  arm.  For  convenience  in 
adding  mercury,  it  is  well  to  set  the  tube  on  the 
floor.  With  a  piece  of  string  fasten  the  tube  upright 
to  some  convenient  support,  as  a  knob  to  a  drawer 
of  your  desk.  From  this  time  on  avoid  as  much 
as  possible  any  heating  of  the  confined  air  from 
contact  with  the  hands  or  other  parts  of  the  body. 
Why  avoid  heating?  Measure  the  length  of  the 
column  of  air  to  be  experimented  on,  i.e.,  the  column 

1  See  foot-note,  page  xxvii  of  the  Introduction. 

2  Dirty  mercury  can  often  be  cleaned  by  treatment  with  a  few  drops 
of  strong  nitric  acid. 


THE   BAROMETER.  127 

in  the  short  tube.  If  the  tube  tapers  at  all  it  should 
be  rejected.  Why?  Allowance  should  be  made  if 
the  end  of  the  tube  is  not  closed  square  across  but  is 
rounded,  as  is  usual.  Note  that  there  is  already  a 
considerable  pressure  on  the  confined  air,  because  the 
whole  pressure  of  the  atmosphere  [equal  to  the  weight 
of  a  column  of  air  directly  over  the  surface  of  the 
mercury  in  the  long  arm,  and  extending  up  as  far  as 
the  air  itself  reaches]  is  exerted  on  the  surface  of  the 
mercury  in  the  open  arm,  and  this  pressure  is  trans- 
mitted by  the  mercury  around  the  bend  to  the  lower 
surface  of  the  confined  air.  Determine,1  as  follows, 
the  amount  of  this  pressure  of  the  atmosphere :  Take 
a  piece  of  glass  tube  at  least  a  meter  long  and  4  or 
5mm  bore.  Heat  the  tube  about  5cm  from  the  end, 
and  draw  off  a  piece  in  order  to  leave  one  end  of  the 
long  tube  closed.  Fill  the  long  tube  within  about 
two  finger-widths  of  the  top  with  mercury.  Put  your 
thumb  over  the  end  and  slowly  invert  the  tube,  letting 
the  big  bubble  of  air  pass  up,  sweeping  along  the  little 
bubbles.  Repeat  the  inversions  till  the  big  bubble  has 
collected  all  the  air  it  can ;  then  fill  the  tube  completely 
with  mercury,  and,  without  letting  any  air  enter,  plunge 
its  open  end  beneath  the  surface  of  mercury  held  in 
some  stout  dish,  as  a  porcelain  mortar.  Support  the 
tube  upright,  and  note  the  formation  of  a  "  Torricelli's 
vacuum"  at  the  top.  The  instrument  you  have  now 

1  If  you  have  a  barometer  this  pressure  can  be  determined  readily 
and  more  accurately  from  this  than  from  the  crude  apparatus  made 
in  this  experiment.  However,  no  part  of  this  experiment  should  be 
omitted,  but  in  the  last  part  it  would  be .  better  to  substitute  the 
reading  of  a  good  barometer  for  the  reading  made  from  your  own. 


128          PERIOD  OF  ROBERT  BOYLE. 

made  will  serve  you  very  well  as  a  barometer,  i.e.,  an 
instrument  for  measuring  the  varying  pressure  of  the 
atmosphere.  The  better  you  have  removed  the  air  from 
the  mercury,  and  the  purer  your  mercury,  the  more 
nearly  will  the  readings  of  your  instrument  approach 
those  of  a  high-grade  barometer.  Measure  the  height 
of  the  column  of  mercury  which  the  air  pressure  is 
able  to  support.  Mercury  is  13.6  times  as  heavy  as 
water.  Estimate  the  pressure  of  air  against  one  square 
centimeter  of  surface.  One  square  centimeter  occupies 
0.155  square  inch.  Estimate,  then,  the  pressure  in 
pounds  against  one  square  inch. 

Air  pressure  is  usually  expressed  simply  by  the 
measurement  of  the  length  of  the  column  of  mercury 
[in  the  barometer]  which  the  air  supports. 

Return  to  your  bent  glass  tube  with  its  volume  of 
confined  air.  Add  mercury  to  the  long  arm  till  the 
surface  of  the  mercury  in  this  arm  is  as  many  centi- 
meters above  the  surface  of  the  mercury  in  the  short 
arm  as  the  surface  of  the  mercury  in  the  tube  of 
the  barometer  stands  above  the  surface  of  the  mer- 
cury in  the  cistern  of  the  barometer,  i.e.,  double 
the  pressure  on  the  confined  air  in  the  short  arm. 
Measure  the  length  of  the  short  column  now,  and 
note  the  effect  that  doubling  the  pressure  has  had 
on  the  size  of  the  volume.  Why  would  it  not  have 
doubled  the  pressure  if  you  had  simply  increased 
the  height  of  the  mercury  in  the  long  arm  by  76cm 
[more  or  less]  above  its  own  original  height,  and  not 
above  the  new  height  of  the  mercury  in  the  other 
arm? 


ELEMENTS.  129 

The.  Law  of  Boyle  may  be  stated  thus.  The  volume 
of  a  gas  is  inversely  proportional  to  the  pressure  to  which 
it  is  subjected,  i.e.,  if  the  pressure  is  doubled  the  volume 
is  halved;  three  times  the  original  pressure  gives  one 
third  the  original  volume,  etc. 

As  to  the  value  of  the  inductive  method,  Boyle 
clearly  stated  that  if  men  really  cared  to  get  at  the 
truth  there  was  no  way  by  which  they  could  benefit 
the  world  more  than  by  going  to  work  and  performing 
experiments,  collecting  observations,  but  not  attempt- 
ing to  propose  theories  till  all  the  phenomena  involved 
had  been  noticed.  From  this  statement,  and  Boyle's 
consistent  practice  of  what  it  teaches,  we  see  that  he 
was  the  first  to  pursue  chemistry  in  a  truly  scientific 
spirit.  That  Boyle  wished  to  establish  chemistry  as  a 
science  independent  of  medicine,  physics  or  any  other, 
and  that  up  to  this  time  chemistry  had  not  been 
regarded  as  a  separate  science,  is  shown  by  his  state- 
ment that  he  found  most  of  the  disciples,  of  chemistry 
had  hardly  any  object  in  view  except  the  preparation 
of  medicines,  or  the  ennobling  of  metals  ;  that  he  him- 
self was  tempted  to  enter  the  art  not  as  a  physician  or 
an  alchemist,  and  that  with  this  in  view  he  drew  up  a 
scheme  of  chemical  philosophy. 

Boyle  saw  that  neither  Aristotle's  theory  of  elements 
nor  the  theories  of  the  alchemists  were  sound.  He 
maintained  that  only  substances  that  cannot  be  decom- 
posed into  simpler  constituents  should  be  regarded  as 
elements ;  that  many  of  the  substances  held  in  his  day 
to  be  simple  would  sometime  be  decomposed  ;  and  that 


130         PEEIOD  OF  ROBERT  BOYLE. 

one  should  not  attempt  to  fix  any  definite  number  for  the 
elements.  A  belief  like  this  shows  what  a  long  step  in 
advance  of  all  previous  chemists  the  clear-sighted  Boyle 
was  able  to  take.  His  views  in  regard  to  the  nature  of 
elements  have  not  been  essentially  modified  to  the 
present  day.1 

In  his  attempts  to  separate  compounds  Boyle  did  so 
much  analytical  work,  and  devised  so  many  processes 
for  separation  and  for  the  recognition  of  the  presence 
of  substances  in  compounds,  that  he  may  be  said  to 
have  founded  the  department  of  chemistry  called  Qual- 
itative Analysis.  It  is  true  that,  during  the  periods 
of  alchemy  and  medical  chemistry,  attempts  had  been 
made  to  get  at  the  constitution  of  bodies,  but  little 
advance  had  been  made  toward  any  systematic  scheme 
for  separation.  It  is  seldom  that  separation  can  be 
made  in  so  simple  a  manner  as  when  red  oxide  of 
mercury  is  converted  by  heat  into  mercury  and  oxygen, 
or  as  we  have  done  in  any  of  those  analyses  noted  on 
pages  107-108. 

Boyle  saw  that  it  is  not  necessary  to  separate  a 
metal,  a  gas,  an  oxide,  from  its  compound  in  order 
to  prove  that  it  is  present,  but  was  able  to  tell  the 
presence  of  substances  by  certain  changes.  He  found 

1  It  may  be  said  that  at  the  present  date  there  seems  some  slight 
reason  to  believe  that  elements  chemically  similar  may  sometime  be 
found  mutually  convertible,  and  that  finally  a  dream  of  the  alchemists 
may,  in  a  measure,  be  realized.  Speculation  is  rife,  and  speculation 
based  on  some  semblance  of  facts,  as  to  the  possible  separation  of  all 
so-called  elements.  That  hydrogen  may  be  found  to  be  the  basis  of 
all,  or  that  an  unknown  element  of  unexpected  simplicity  may  be 
found  a  component  of  all,  hydrogen  included,  has  even  been  suggested 
by  chemists  of  repute. 


QUALITATIVE   TESTS.  131 

that  when  a  solution  of  a  calcium  salt  is  added  to  a 
solution  containing  sulphuric  -  acid,  or  a  solution  of  a 
silver  salt  added  to  one  containing  hydrochloric  acid, 
a  white  precipitate  is  caused.  By  means,  then,  of 
calcium  and  silver  salts,  he  was  able  to  test  for  sul- 
phuric and  hydrochloric  acids,  respectively ;  and  by 
means  of  these  two  acids,  conversely,  he  tested  for 
calcium  and  silver  salts.  He  tested  for  ammonia  with 
the  vapors  of  hydrochloric  acid,  the  production  of  a 
white  cloud  proving  its  presence.  He  also  made  use  of 
plant  extracts,  as  those  from  litmus,  violet,  cornflower, 
etc.,  in  testing  for  acids  and  alkalies.  He  used  his 
plant  juices  both  in  solution  and  on  papers  as  we  do 
still.  To  this  use  of  "tests"  Boyle  first  applied  the 
name,  ever  since  kept,  Analysis.1 

In  the  practice  of  Qualitative  Analysis  at  the  present 
day  the  chemist  does  not  generally  isolate  substances 
in  order  to  prove  them  present,  but,  like  Boyle,  uses 
certain  "tests,"  i.e.,  he  brings  about  a  series  of  chem- 
ical changes,  from  an  inspection  of  which  he  is  able  to 
judge  what  substances  are  present  without  ever  having 
seen  them.  During  the  last  hundred  years  observa- 
tions have  been  greatly  multiplied  and  systems  of  pro- 
cedure devised  so  that  Qualitative  Analysis  to-day 
requires,  on  the  part  of  the  analyst,  a  familiarity  with 
a  vast  number  of  changes,  a  knowledge  of  when,  and 
in  what  order  these  should  be  brought  about,  and  an 
ability  to  interpret  their  results. 

1  Assaying  would  be  a  better  term  to  use  for  this  testing,  because 
this  testing  is  seldom  strictly  analyzing. 


132         PERIOD  OF  ROBERT  BOYLE. 

Experiment  1O. 

Qualitative  Tests. 
A.   Tests  used  by  Boyle. 

First  prepare  re-agents,  or  test  solutions,  as  follows: 
[Each  solution  should  be  kept  in  a  clean,  stoppered 
bottle,  or  flask.] 

I.  Sulphuric  acid.       To   20CC  of  water  add  lcc  of 
sulphuric  acid. . 

II.  Hydrochloric  acid.      To  15CC  of  water  add  lcc 
of  the  strongest  laboratory  hydrochloric  acid  solution. 

III.  Silver  salt.     To  20CC  of  water  add  half  a  gram 
of  nitrate  of  silver.     Shake  till  the  nitrate  dissolves. 

IV.  Calcium  salt.     To  20CC  of  water  add  6  grams 
of  chloride  of  calcium.     Shake  till  solution  takes  place. 
If  the  solution  is  not  clear,  filter  into  a  narrow-necked 
bottle. 

In  a  tt  containing  a  few  cc  of  I  drop  a  little  of  IV. 
Note  formation  of  a  white  precipitate.  Try  a  similar 
experiment,  mixing  some  of  II  with  some  of  III. 

H.     Tests  by  Physical  Changes. 

Take  a  piece  of  glass  rod,  heat  one  end  till  it  softens, 
fasten  in  a  piece  of  platinum  wire  about  5cm  long,  and 
make  a  loop  in  the  end  of  the  wire.  Moisten  the  loop, 
and  take  up  a  little  chloride  of  potassium.  Using  the 
glass  rod  as  a  handle,  hold  the  chloride  in  the  flame 
of  the  Bunsen  burner  and  note  the  flame  coloration. 
Remove  all  chloride  from  the  wire,  testing  it  in  the 
flame  to  make  sure  no  trace  is  left;  and  in  the  same 
way  note  the  flame  coloration  produced  by  chloride  of 


CHEMICAL   TESTS.  133 

lithium,  by  chloride  of  sodium,  by  chloride  of  barium. 
The  colors  here  seen  are  "characteristic,"  i.e.^  they 
indicate  to  the  chemist  the  presence  of  the  metals, 
potassium,  lithium,  sodium,  barium,  respectively,  in  the 
substances  tested.1 

C.     Tests  by  Chemical  Changes. 

Have  ready  four  tts  labeled  «,  5,  c,  d.  Put  a  bit 
of  silver  in  a,  a  bit  of  lead  in  5,  a  bit  of  copper  in  e,  a 
bit  of  white  arsenic  in  d.  In  each  case  the  amount 
of  the  substance  should  not  be  larger  than  a  small  pea. 
Add  to  every  tt  about  lcc  of  nitric  acid,  and  warm  till 
solution  takes  place.  Add  about  10CC  of  water  to  every 
tube.  Divide  every  one  of  the  four  solutions  into  two 
portions,  putting  part  in  other  tubes  labeled  a\  b\  c\  d\ 
corresponding  to  a,  5,  c,  d,  respectively.  To  every  one 
of  the  solutions,  #,  5,  <?,  d,  add  a  few  drops  of  hydro- 
chloric acid  solution.  Note  effect.  Heat  the  solutions 
in  which  hydrochloric  acid  causes  a  precipitate.  Note 
effect.  Cool.  Note  effect.  To  the  solutions  not  pre- 
cipitated by  hydrochloric  acid  add  aqua  ammonia  till 
alkaline  to  test  papers.  Note  effect.  Into  the  solu- 
tion still  unchanged  pass  sulphide  of  hydrogen  gas. 
Note  effect.  Record  all  observations  in  the  form  of  a 
table  in  the  note-book.  Note  that  hydrochloric  acid 
was  a  characteristic  test  for  both  silver  and  lead,  giving 
with  silver  an  insoluble  white  precipitate,  with  lead  a 
white  precipitate  soluble  when  heated;  that,  after  the 

1  If  the  laboratory  possesses  a  spectroscope,  examine  the  four  flames 
through  this  instrument,  and  map  in  your  note-book  the  lines  seen  in 
each  case. 


134         PERIOD  OF  ROBERT  BOYLE. 

addition  of  hydrochloric  acid  had  proved  there  was 
neither  silver  nor  lead  in  c,  the  blue  color  produced 
by  ammonia  was  a  test  for  copper ;  and  that,  when 
the  absence  of  silver,  lead,  and  copper  had  been  proved 
in  d,  the  production  of  a  lemon-colored  precipitate,  by 
sulphide  of  hydrogen,  was  a  test  for  arsenic. 

But  for  the  successful  practice  of  qualitative  analysis, 
the  chemist  must  know  not  only  what  tests  to  use,  but  in 
what  order  the  proper  tests  are  to  be  used.  In  order 
to  see  that  this  is  so,  to  the  solutions  numbered  a\  b\ 
c\  d\  at  once  pass  in  sulphide  of  hydrogen,  i.e.,  use  the 
last  re-agent  first.  Note  that  here  you  get  three  black 
precipitates  about  alike  in  color,  solubility,  etc.,  and  no 
distinction  is  possible. 

At  the  present  day  there  are  about  seventy  sub- 
stances which  resist  every  effort  of  the  chemist  at 
separation.  These  are  called  the  elements,  but  it  is 
by  no  means  certain  that  some,  if  not  all,  may  not  be 
separated  when  we  have  better  means  of  analysis,  or 
more  knowledge  to  apply  the  means  we  do  have. 

The  most  commonly  occurring  elementary  substances 
are  the  following : 

Aluminum,  Gold,  Oxygen, 

Antimony,  Hydrogen,  Phosphorus, 

Arsenic,  Iodine,  Platinum, 

Barium,  Iron,  Potassium, 

Bismuth,  Lead,  Silver, 

Bromine,  Magnesium,  .       Sodium, 

Calcium,  Manganese,  Sulphur, 

Carbon,  Mercury,  Tin, 

Chlorine,  Nickel,  Zinc. 

Copper,  Nitrogen, 


MIXTURES   AND   COMPOUNDS.  135 

For  a  complete  list  of  the  elements  at  present  recog- 
nized, see  page  216. 

Boyle  even  proposed  a  theory  that  was  far  in  advance 
of  any  previous  chemical  theory.  His  theory  was  that 
matter  is  made  up  of  small  particles  —  corpuscles ;  that 
a  chemical  compound  results  from  a  mutual  attraction 
of  the  particles  when  particles  of  certain  kinds  of  matter 
come  together.  Moreover,  no  one  before  had  stated 
clearly,  as  he  now  did,  that  a  chemical  compound  is 
formed  by  the  union  of  two  or  more  factors,  and  that 
the  compound  itself  has  properties  entirely  different 
from  either  factor.  He  distinguished  correctly  between 
a  mere  mixture  and  a  chemical  compound. 


Experiment  11. 
Mechanical  Mixture  and  Chemical  Compound. 

Not  every  mixing  of  substances  results  in  the  forma- 
tion of  a  true  chemical  compound. 

A.     Iron  and  Sulphur. 

Weigh  out,  of  very  fine  iron  filings,  56  decigrams ; 
of  flowers  of  sulphur,  32  decigrams.  Grind  the  two 
well  together  in  a  mortar  till  the  eye  can  no  longer 
distinguish  the  separate  particles  of  either  substance, 
and  the  mass  looks  homogeneous.  Apply  a  magnet, 
and  note  that  the  iron  may  be  separated  from  the 
sulphur.  Again  grind  together,  and  put  the  mixture 
in  a  large  tt.  Heat  well  over  a  Bunsen  flame.  Break 
the  tt,  and  examine  the  product.  Grind  in  a  mortar,  and 


136          PERIOD  OF  ROBERT  BOYLE. 

again  apply  the  magnet.  Note  that  no  separation  can 
now  be  made,  for  one  particle  seems  attracted  as  much, 
or  as  little,  as  every  other.  The  substance  formed  is  a 
compound,  and  one  particle  has  the  same  properties  as 
every  other.  What  is  this  compound?  What  were 
the  factors  ? 

B.     Zinc  and  Sulphur. 

Caution !  In  mixing  the  zinc  and  the  sulphur  for 
this  experiment  do  not  grind  them  in  a  mortar,  as 
pressure  alone  is  capable  of  producing  the  chemical 
union  with  explosive  suddenness. 

With  a  spatula,  mix,  as  intimately  as  possible,  65 
decigrams  of  zinc  dust  and  32  decigrams  of  flowers 
of  sulphur.  Put  some  of  this  powder  under  a  micro- 
scope and  note  that  combination  has  not  taken  place, 
as  the  gleaming,  dark-colored  pieces  of  zinc  may  be 
distinguished  from  the  irregular,  somewhat  smutted 
[by  the  zinc  powder]  granules  of  sulphur.  Heap  the 
greater  part  of  the  mixture  on  a  brick,  stone,  or  some 
other  substance  not  harmed  by  heat,  and  set  fire  to  it. 
Note  phenomena.  Examine  with  a  microscope  some 
of  the  product  where  the  change  has  been  complete. 
Can  you  see  either  zinc  or  sulphur?  What  kind  of 
a  change  has  taken  place  ?  What  caused  the  change  ? 
What  did  the  chemical  change  itself  cause?  What 
did  the  heat  cause? 

The  simplicity  and  clearness  of  Boyle's  writings 
form  a  pleasing  contrast  to  the  self-laudatory  works 
of  Paracelsus,  the  contradictory  ones  of  Van  Helmont, 
and  the  generally  obscure  writings  of  most  of  the  other 


CHEMISTRY   A   TBUE    SCIENCE.  137 

medical  chemists  and  the  alchemists.  Robert  Boyle 
was  a  seeker  after  the  truth.  Where  he  did  not  him- 
self see  clearly  he  never  attempted  to  deceive  by  involv- 
ing his  reader  in  doubt  and  obscurity.  Animated  by 
the  spirit  of  pure  investigation,  he  placed  scientific 
speculation  on  that  sure  foundation  —  experimentation 

-  upon  which  it  has  ever  since  so  securely  rested. 

From  the  time  of  Boyle,  chemistry  has  been  dependent 
upon  neither  medicine,  physics,  nor  any  other  science, 
but  has  of  itself  been  a  true  science  with  the  solution 
of  a  definite  problem  —  the  composition  of  substances 

—  as  its  goal,  and  a  method  —  the  inductive  —  both 
systematic  and  logical,  its  means  for  attaining  the 
wished-for  goal.  Boyle,  too,  gave  chemistry  its  highest 
aim  —  the  pursuit  of  absolute  Truth. 

For  Review.  When  did  Boyle  live  ?  State  the  law 
of  Boyle.  What  three  important  services  did  he  render 
chemistry  ?  How  did  he  define  an  element  ?  To  what 
did  he  apply  the  term  analysis  ?  State  one  of  Boyle's 
analytical  tests.  Describe  some  chemical  tests  by  means 
of  physical  changes.  Describe  a  series  of  tests  by  means 
of  chemical  changes.  How  many  elements  are  now 
recognized?  Mention  the  most  commonly  occurring 
elementary  substances.  What  theory  did  Boyle  pro- 
pose to  explain  chemical  changes?  Distinguish  between 
a  mere  mixture  and  a  chemical  compound.  Upon  what 
foundation  did  Boyle  rest  his  speculations  ?  What  high 
aim  did  he  give  chemistry  ? 


138  THE   PHLOGISTON    PERIOD. 

CHAPTER  VI. 

THE    PHLOGISTON    PERIOD. 

This  period,  in  which  the  attention  of  chemists  was 
directed  mainly  to  the  explanation  of  combustion,  may 
be  said  to  cover  the  eighteenth  century.  It  began, 
however,  even  before  Boyle's  death,  in  Becher's  theory, 
that  when  substances  were  burned,  a  terra  pinguis,  as 
he  called  it,  passed  off.  Stahl,1  who  worked  —  chiefly 
at  Berlin  —  during  the  early  part  of  the  eighteenth 
century,  was  the  chief  developer  of  the  phlogiston 
theory.  Stahl  believed  that  all  combustible  bodies, 
metals  rightly  included,  contained  within  them  a  sub- 
stance which  he  called  phlogiston,  and  that  this 
substance  passed  off  when  combustion  took  place, 
and  returned  when  such  substances  as  we  call  oxides, 
e.g.,  red  oxide  of  mercury,  black  oxide  of  iron,  etc., 
were,  as  we  say,  reduced.  Substances  which  burned 
vigorously  he  thought  contained  much  phlogiston, 
while  those  which  leave  little  residue  after  combus- 
tion, as  coal  and  soot,  he  thought  to  be  made  of  nearly 
pure  phlogiston.  According  to  this  theory  metals  were 
compounds,  while  their  oxides  were  of  simpler  form  — 
one  factor,  phlogiston,  having  departed. 

It  is  hard  to  see  how  the  fact  that  the  residues  from 
burning  the  metals  are  heavier  than  the  metals,  and 
consequently,  addition,  and  not  subtraction,  takes  place 
in  combustion,  escaped  the  notice  of  Stahl.  To  be 
sure,  his  mind  was  chiefly  intent  on  such  cases  as  the 

1  Stahl  lived  1660-1734. 


END    OF    THE    PHLOGISTON    THEORY.  189 

burning  of  wood,  coal,  etc.,  in  which  the  fact  that  there 
is  great  weight  to  the  gases  that  pass  off  was  then  all 
unknown.  A  little  later  attention  was  called  to  the 
fact  that  residues  from  the  combustion  of  metals  do 
weigh  more  than  the  metals  themselves.  This  diffi- 
culty in  the  way  of  the  phlogiston  theory  was  met  by 
some  who  assumed  that  phlogiston  was  the  principle 
of  absolute  lightness,  i.e.,  that  phlogiston  had  a  neg- 
ative weight,  and  so  when  it  was  removed  from  a 
substance,  the  substance  naturally  gained  in  weight ; 
and  by  others  —  who  simply  ignored  it.  But  after  the 
fact  that  the  products  of  combustion  do  weigh  more 
than  the  combustibles  had  repeatedly  thrust  itself  on 
the  attention  of  chemists,  and  after  gases  had  been 
more  carefully  studied  [in  the  pneumatic  period],  it 
became  evident  that  the  theory  of  phlogiston  had  fatal 
weaknesses.  Its  death  blow  came  in  1783,  when, — the 
true  nature  of  both  oxygen  and  hydrogen  gases  having 
been  pointed  out,  also  the  fact  that  water  consists  of 
these  two  substances  united,  —  the  part  that  oxygen 
plays  in  combustion  was  proved.  To  be  sure,  some 
chemists — notably  Priestly1  and  Cavendish,  whose  very 
works  did  much  to  destroy  the  phlogiston  theory  — 
vehemently  denied,  even  till  the  end  of  the  century, 
and  beyond,  that  this  cherished  theory  was  dead. 

For  Review.  State  the  phlogiston  theory.  Who 
developed  this  theory  ?  When  ?  How  was  combustion 
explained  by  the  phlogiston  theory?  How  reduc- 
tion? What  important  fact  did  the  phlogistonists 
either  neglect  or  explain  in  an  absurd  manner? 

1  Priestly  has  been  called  one  of  the  fathers  of  modern  chemistry, 
but  it  has  also  been  said  that  he  was  "  un  pere  qui  ne  voulut  jamais 
reconnoitre  sa  fille." 


140  PNEUMATIC    PERIOD. 

CHAPTEE   VII. 

PNEUMATIC    PERIOD. 

We  may  apply  the  name  pneumatic  to  an  important 
period  which  immediately  preceded  the  last  or  modern 
period  of  chemistry.  The  name  pneumatic  is  derived 
from  a  Greek  word  meaning  air  or  wind.  It  is  applied 
to  that  period  of  chemistry  in  which  the  attention  of 
chemists  was  devoted  chiefly  to  a  study  of  gaseous  sub- 
stances. The  pneumatic  period  is  over-lapped  by  that 
of  phlogiston,  and  even  by  the  medical,  for  we  found 
that  Van  Helmont  worked  with  aeriform  matter,  and, 
in  fact,  he  is  sometimes  spoken  of  as  the  founder  of 
pneumatic  chemistry.  He  first  pointed  out  the  dis- 
tinction between  various  kinds  of  gases,  as  carbonic 
dioxide,  sulphurous  oxide,  etc.,  and  it  was  he  who  gave 
us  the  name  "  gas  "  for  aeriform  matter  which  does  not, 
on  cooling  to  the  ordinary  temperature,  take  the  liquid 
state.  Boyle  was  preeminently  noted  for  his  investiga- 
tion of  gases,  but  neither  he  nor  his  contemporaries 
were  able  to  distinguish  between  hydrogen  and  car- 
bonic dioxide,  both  of  which  they  thought  were  modified 
forms  of  air. 

It  was  Black,1  who  lived  one  hundred  years  later 
than  Boyle,  who  proved  the  difference  between  air  and 
carbonic  dioxide.  He  noticed  that  when  carbonates  of 
magnesium  or  of  lime  are  heated,  a  gas,  identical  with 
Van  Helmont's  gas  sylvestre,  goes  off,  and  the  carbonate 

1  Joseph  Black,  born  in  1728,  died  in  1799,  was  professor  of  chem- 
istry at  Glasgow  and  Edinburgh. 


SPECIFIC    GRAVITY    OF   AIR.  141 

loses  in  weight.  He  found  that  what  were  then  called 
caustic  alkalies  [our  caustic  hydroxides],  are  capable  of 
taking  up  this  gas  and  becoming  what  were  then  called 
mild  alkalies  [our  carbonates].  Owing  to  this  fixation 
of  the  gas  he  gave  it  the  name  of  fixed  air. 

Cavendish1  came  soon  after  Black,  and  contributed 
so  much  to  our  knowledge  of  gases  that  he  has  been 
called  the  father  of  pneumatic  chemistry.  To  him  we 
owe  the  pneumatic  trough,  and  he  pointed  out  the 
necessity  for  making  accurate  determinations  of  the 
relative  weights,  or  specific  gravities,  of  different  gases, 
in  order  to  distinguish  one  gas  from  another. 

Let   us   determine    the    specific    gravities   of   some 


Experiment  12. 
Weight  and  Specific  Gravity  of  Air.2 

Take  a  large  [2-4  liter]  "  prescription  bottle."  3  Make 
sure  it  is  perfectly  dry  and  clean.  Fit  it  with  a  one- 
hole  rubier  stopper  through  which  passes  a  short  piece 
of  tightly-fitting  glass  tube  carrying  a  bit  of  rubber  tube 
fitted  with  a  pinch-cock.  Insert  the  stopper,4  with  its 
tube,  close  the  pinch-cock,  and  weigh  the  bottle,  tubes 

1  Henry  Cavendish,  born  1731,  died  1810,  was  an  English  chemist 
and  physicist,  very  wealthy  and  very  bashful. 

2  See  foot-note,  page  xxvii  of  the  Introduction. 

3  A  cheap,  stout,  narrow-necked  bottle. 

4  In  this  experiment  to  make  the  joints  air-tight,  it  is  well  to  smear 
the  stopper  and  all  rubber  connectors  with  glycerine  or  vaseline.     Be 
sure,  however,  that  all  greasing  is  done  before  the  first  weighing. 


142  PNEUMATIC    PERIOD. 

and  all,  full  of  air.  With  a  small  air-pump  *  draw  from 
the  bottle  as  much  air  as  you  can.  Close  the  rubber 
tube  with  the  pinch-cock,  again  weigh  the  bottle  with 
its  fittings,  and  note  the  loss  in  weight.  What  has 
caused  the  loss?  Now  get  the  volume  of  air  removed 
as  follows  :  Have  ready  a  pail,  or  tub,  of  water.  Open 
the  pinch-cock  with  the  end  of  the  rubber  tube  well 
under  water.  What  causes  the  water  to  rush  in? 
Lower  the  bottle  in  the  water  till  the  wrater  inside  and 
outside  is  on  the  same  level.  Why  on  the  same  level  ? 
Close  the  pinch-cock,  wipe  the  bottle  dry,  and  weigh 
on  the  platform  balances  [accurately  to  1  gram  only]. 
Remembering  that  1  gram  of  water  equals  lcc,  get  the 
volume  of  the  water  which  has  entered,  i.e.,  the  volume 
of  the  air  which  was  pumped  out. 

Find  the  weight  of  lcc  of  air  in  the  room,  at  the  time 
of  doing  the  experiment.  This,  then,  is  the  density  of 
air,  the  density  of  any  substance  being  the  weight  of 
a  unit  volume  of  that  substance.  The  specific  gravity 
of  a  substance  is  the  number  of  times  heavier  a  given 
volume  of  that  substance  is  than  an  equal  volume  of 
some  substance  taken  as  a  standard.  Water  is  often 
taken  as  the  standard  substance.  If  lcc  of  water  weighs 
1  gram,  calculate  the  specific  gravity  of  air  referred  to 
water.  Calculate  the  weight  of  air  in  a  room  15  meters 
long,  13  meters  wide,  and  7  meters  high.  After  you 
get  the  weight  in  grams  get  it  in  pounds,  assuming  that 
1  pound  is  equivalent  to  453.6  grams. 

1  Small  pumps  like  those  often  used  for  inflating  the  tires  of  bicycles, 
serve  well  for  this  purpose,  provided  they  have  check-valves  for  exhaus- 
tions. 


THE   LAW   OF   D ALTON.  143 

Note  that  air,  as  well  as  every  other  gas,  is  an  elastic 
body,  which  can  be  compressed  into  smaller  space  by 
pressure  [see  Ex.  9,  the  Law  of  Boyle].  The  greater 
the  pressure,  the  greater  the  amount  of  air  in  a  given 
volume,  hence  the  greater  the  density.  If,  then,  other 
things  being  equal,  you  filled  your  bottle  with  air  when 
the  barometer  stood  high,  i.e.,  when,  owing  to  atmos- 
pheric conditions,  the  pressure  on  the  air  at  the  surface 
of  the  earth  was  great,  you  would  get  a  greater  density 
for  the  air  than  you  would  had  the  barometer  stood 
low. 

The  density  of  a  gas  is  also  affected  by  the  tempera- 
ture. As  is  well  known,  the  higher  the  temperature 
the  greater  the  volume  of  a  given  weight  of  gas,  and  the 
lower  the  temperature  the  less  the  volume.  The  expres- 
sion of  the  exact  rate  at  which  a  gas  volume  decreases 
when  the  temperature  is  lowered  [or  increases  when 
it  is  raised],  is  called  the  Law  of  Dalton,  from  John 
Dalton,  who  seems  to  have  been  the  first  to  state  this 
law  clearly.1 


Experiment  13. 
The  Law  of  Dalton.2 

Have  ready  a  250CC  flask  fitted  with  a  one-hole  rubber 
stopper.  Also  have  ready  about  25 cm  of  glass  tube  to 
fit  the  hole  in  the  stopper,  also  about  25cm  of  rubber- 
tube  to  fit  the  glass  tube,  also  a  pinch-cock  to  close  the 

1  This  law  is  also  called  the  Law  of  Charles,  from  a  Parisian  investi- 
gator, who  is  said  to  have  discovered  it. 

2  See  foot-note,  page  xxvii  of  the  Introduction. 


144  PNEUMATIC   PERIOD. 

end  of  the  rubber  tube.     It  is  necessary  to  have  ice  or 
snow  for  this  experiment. 

Make  sure  the  flask  and  all  tubes  are  dry.  Insert 
the  glass  tube  through  the  stopper.  Let  the  glass  tube 
reach  nearly  to  the  bottom  of  the  flask  and  protrude  only 
about  1  inch  from  the  stopper.  Connect  the  rubber 
tube  with  the  glass  tube.  Let  the  pinch-cock  be  placed 
at  the  extreme  end  of  the  rubber  tube  farthest  from  the 
stopper.  Why?  Have  ready  a  vessel  of  warm  water. 
Insert  the  stopper  in  the  flask.  Open  the  pinch-cock 
and  plunge  the  flask  beneath  the  water,  but  do  not  let 
any  water  get  into  the  flask  or  tubes.  Why?  Bring 
the  water  to  the  boiling  point,  — 100°  centigrade. 
When  the  flask  is  wholly  immersed  in  boiling  water 
close  the  pinch-cock  and  remove  the  flask  from  the  water 
bath.  Keep  your  eyes  away  as  the  flask  may  burst. 
When  cool,  open  the  pinch-cock  with  the  end  of  the 
tube  under  iced  water.  When  as  much  water  as  pos- 
sible has  entered,  close  the  cock.  Make  an  ice-water 
bath  [with  much  floating  ice]  of  your  hot-water  bath, 
and  return  the  flask.  Have  at  hand  a  beaker  contain- 
ing ice-water,  in  which  much  melting  ice  is  floating. 
Again  open  the  cock,  with  the  end  of  the  tube  under 
the  surface  of  the  ice-water  in  the  beaker.  Keeping 
the  flask  well  under  the  cold  water,  make  the  level 
of  the  water  in  the  flask  and  that  of  the  water  in 
the  beaker  the  same  [by  raising  or  lowering  the 
beaker],  and  close  the  cock.  Remove  the  flask  from 
the  ice  bath.  Loosen  the  stopper,  open  the  cock, 
and  let  the  water  in  the  tubes  run  into  the  flask. 
Why?  Get  the  volume  of  the  water  in  the  flask. 


OJ  TOT 


SP.    GV.    OF    CARBONIC  DIOXIDE. 

*    :. 

Also  get  the  total  contents  of  the  flask  [when  the 
tube  is  in  it].  From  the  data  thus  prepared,  calcu- 
late [a]  the  volume  of  the  air  experimented  on  at  0°  ; 
[b]  its  volume  at  100°  ;  [c]  the  amount  the  volume  at 
0°  would  expand  in  going  to  100°;  [d]  the  amount  it 
would  expand  in  going  1°  ;  and,  finally,  [e]  the  amount 
that  unit  volume  would  expand  in  going  1°.  This 
last  numerical  value  is  called  the  coefficient  of  expan- 
sion. It  should  come  out  about  0.00366  or  ^fa.  If 
lcc  of  gas,  measured  at  0°,  loses  or  gains  -%\-%  of  its 
volume  for  every  degree  cooled  or  heated,  respectively, 
at  what  temperature  does  it  become  2CC  ?  What  would 
be  the  volume  of  lcc  of  gas,  measured  at  0°,  if  cooled 
to  -  273°  ?  What  is  the  point  -  273°  called  ? 

The  Law  of  Dalton  may  be  stated  thus.  The  volume 
of  a  gas  varies  directly  as  the  temperature  on  the  abso- 
lute scale,  i.e.,  a  scale  having  its  0°  point  273°  below 
0°  C.,  its  273°  mark  at  0°  C.,  its  373°  mark  at  100°  C., 
etc.  Or  the  law  may  be  stated  thus.  TJie  volume  of  a 
gas  measured  at  0°  C.  increases  [or  decreases],  by  ^\-%  of 
itself  for  every  degree  0.  that  the  temperature  increases 
[or  decreases]. 

Experiment  14. 
Weight  and   Specific  Gravity  of  Carbonic  Dioxide.1 

Note.  In  comparing  the  weights  of  gases,  air,  more 
frequently  than  water,  is  taken  as  a  standard  substance. 
The  comparison,  also,  is  usually  made  at  what  are 
called  standard  conditions,  i.e.,  when  the  temperature 

1  See  foot-note,  page  xxvii  of  the  Introduction. 


146  PNEUMATIC   PERIOD. 

is  0°  C.  and  the  barometer  is  760mm.  The  expression 
"standard  conditions"  is  often  expressed  by  N.  T.  P., 
i.e..  Normal  Temperature  and  Pressure.  The  weight 
of  lcc  of  air  at  N.  T.  P.  is  O.OO1293g.  In  deter- 
mining the  specific  gravity  of  a  gas,  the  weight  of  a 
known  volume  is  determined,  then,  by  the  laws  of 
Boyle  and  of  Dalton,  the  volume  which  this  weight 
would  occupy  under  standard  conditions  calculated, 
and  from  these  figures  the  density  is  determined. 

Have  ready  as  large  a  flask  as  will  ride  on  your 
small  balance.  The  flask  should  be  fitted  with  a  one- 
hole  rubber  stopper,  through  the  hole  of  which  passes 
a  tightly-fitting  piece  of  glass  tube  long  enough  to 
reach  to  the  bottom  of  the  flask  and  to  project  an  inch 
or  so  from  the  top  of  the  stopper.  The  outer  end  of 
the  glass  tube  should  carry  an  inch  or  so  of  rubber 
tube  with  a  pinch-cock.  All  joints  should  be  made 
air-tight  with  vaseline  or  glycerine,  but  there  should 
be  no  superfluous  grease.  Fit  the  stopper  to  the 
flask,  fill  completely  to  the  pinch-cock  with  water  and 
measure  the  contents  in  cc.  Clean  and  dry  the  flask, 
making  sure  no  water  lurks  in  the  tubes  or  at  the 
joints.  Loosen  the  stopper  so  that  air  can  pass  in  or 
out  freely,  but  do  not  remove  the  stopper  from  the 
flask.  Set  the  flask  thus  fitted  on  the  pan  of  the 
delicate  balance.  On  the  other  pan  set  a  second  flask 
of  the  same  size  closed  by  a  solid  stopper.  Why?  Add 
any  additional  weight  necessary,  to  one  side  or  the  other, 
for  a  perfect  equilibrium.  Note  the  temperature  close 
to  the  flask  and  take  the  barometer  reading.  From 


SP.    GV.    OF   CARBONIC   DIOXIDE.  147 

the  known  volume  of  the  flask,  calculate,  bearing  in 
mind  the  laws  of  Boyle  and  of  Dalton,  the  weight 
of  air  which  the  open  flask  holds,  thus :  — 

Let  W  =  weight  of  the  air.         Let  H  —  height  of  barometer. 
V  =  volume  as  measured.  x  =  volume  at760mm  [and  t~\. 

t  =  temperature.  y  =  volume  at  760mm  and  0°. 

V  :-x  :  :  760  :  H.  x  :  y  :  :  273  +  t  :  273. 

Therefore  x  =  ^^  Therefore  y  =  |^-|^ 

As  the  weight  of  lcc  of  air  at  N.  T.  P.,  or  0°  and  760mm, 
is  0.001293s,  W  -  y  times  0.001293. 

Note.  If  weights  to  the  amount  of  the  weight  of 
air  that  fills  the  flask  are  placed  on  the  scale  with  the 
flask  and  all  the  air  pumped  out  of  the  flask,  the  flask 
and  its  counterpoise  will  still  balance. 

Prepare  carbonic  dioxide  from  marble  and  hydrochloric 
acid.  Pass  it  first  through  water  and  then  through  sul- 
phuric acid  to  purify  it.  [Use  catch-bottles.]  Pass  the 
gas  through  the  rubber  and  the  glass  tubes  into  the  flask 
till  a  match,  held  where  the  stopper  is  loosened,  is  extin- 
guished. Insert  the  stopper,  close  the  pinch-cock,  and 
remove  the  oxide  generator.  Open  the  pinch-cock  for 
an  instant  to  let  out  any  excess  of  gas.  Close  it  again. 
Note  the  temperature  close  to  the  flask,  take  height  of 
barometer,  and  find  the  gain  in  weight  of  the  flask. 
To  make  sure  the  flask  is  full  of  carbonic  dioxide, 
again  pass  in  the  gas,  for  five  minutes,  and  proceed  as 
before.  If  there  is  any  further  gain  in  weight  the 
flask  was  not  full  the  first  time,  and  you  must  again 
pass  in  the  gas  for  five  minutes,  and  so  continue  till 


148  PNEUMATIC    PERIOD. 

there  is  no  further  gain.  This  weighing,  and  pass- 
ing, and  weighing  again,  is  called  weighing  to  constant 
weight.  When  you  have  got  the  weight  constant, 
again  take  temperature  and  pressure.  The  gain  in 
weight,  plus  the  weight  of  the  air  the  flask  held,  is  the 
weight  of  the  carbonic  dioxide  at  the  observed  tempera- 
ture and  pressure.  From  the  weight  of  the  carbonic 
dioxide  calculate  what  would  be  the  weight  of  the  same 
volume  if  the  temperature  were  zero  and  the  pressure 
760mm,  remembering  that  the  weight  of  a  given  volume 
of  gas  varies  directly  as  the  pressure  and  inversely  as 
the  temperature  on  the  absolute  scale.  The  density, 
then,  of  carbonic  dioxide  —  i.e.,  the  weight  of  lcc  — 
under  standard  conditions,  is  found  by  dividing  the 
weight  of  the  gas,  at  N.  T.  P.,  by  the  volume  of  the 
flask.  Then  the  density  of  carbonic  dioxide  at  N.  T.  P. 
divided  by  the  density  of  air  at  N.  T.  P.  [0.001293] 
gives  the  specific  gravity  of  carbonic  dioxide  referred 
to  air. 


Experiment  15. 
Weight  and  Specific  Gravity  of  Hydrogen  Gas.1 

In  a  similar  manner  to  that  of  the  last  experiment, 
determine  the  specific  gravity  of  hydrogen  gas. 

Caution !  Have  no  fire  near  when  doing  this  experi- 
ment. Be  sure  the  hydrogen  is  pure  and  dry.  It  is 
best  to  pass  the  hydrogen  through  at  least  three  catch- 
bottles, —  the  first  containing  a  solution  of  sodium 

*  See  foot-note,  page  xxvii  of  the  Introduction. 


SP.    GV.    OF   ILLUMINATING    GAS.  149 

hydroxide,  the  others  sulphuric  acid.  Pass  in  a  large 
and  rapid  stream  of  hydrogen  in  order  to  fill  the  flask 
completely. 

Note  that  hydrogen  is  14.37  times  lighter  than 
air.  As  hydrogen  is  the  lightest  gas  known,  it  is 
most  often  taken  as  the  standard  substance  for  specific 
gravity  determinations  in  the  case  of  gases  and  vapors. 
Calling  the  sp.  gv.  of  hydrogen  unity,  calculate  [from 
the  data  of  Experiment  14]  the  sp.  gv.  of  carbonic 
dioxide  referred  to  hydrogen. 


Experiment  16. 
Weight  and   Specific   Gravity  of  Illuminating-  Gas.1 

Take  the  gas  from  the  gas-burner  tap.  Do  not  have 
an  explosion.  Proceed  as  in  the  previous  experiment. 
Get  the  sp.  gv.  referred  to  water,  to  air,  to  hydrogen. 

The  above  method  can  be  used  for  vapor  density 
determinations,  i.e.,  for  determining  the  specific  gravity 
of  substances  that  are  commonly  solids  or  liquids,  but 
which,  by  heat,  can  be  converted  into  vapors.  For 
such  determinations,  of  course,  the  flask  must  be  im- 
mersed in  a  suitable  bath  [as  one  of  air,  paraffine  or 
oil],  which  can  be  heated ;  and  instead  of  filling  by 
passing  in  vapor,  it  is  better  to  put  a  little  of  the 
substance  in  the  liquid  [or  solid]  form  in  the  bottom 
of  the  flask  where  the  heat  of  the  bath  will  convert  it 
into  vapor,  the  excess  of  which  must  be  allowed  to 

1  See  foot-note,  page  xxvii  of  the  Introduction. 


150  PNEUMATIC   PERIOD. 

escape,  leaving  the  flask  exactly  full  of  vapor  at  the 
moment  the  tube  is  sealed  and  the  temperature  of  the 
bath  and  the  air  pressure  determined. 

As  every  gas  has  its  own  particular  specific  gravity, 
a  determination  of  specific  gravity  is  an  excellent 
method  for  distinguishing  one  gas  from  another,  and 
for  telling  whether  a  given  body  of  a  known  gas  con- 
tains an  admixture  of  another  gas  or  not. 

One  of  the  most  important  problems  presented  to 
the  chemists  in  the  pneumatic  period  was  the  compo- 
sition of  our  atmosphere  —  was  it  to  be  considered  a 
simple  substance,  a  compound,  or  a  mixture  of  two  or 
more  ingredients?  The  problem  was  solved,  inde- 
pendently, by  two  of  the  most  eminent  workers  of  the 
time,  Priestly,1  an  English  clergyman,  and  Scheele,2  a 
poor  Swedish  apothecary.  The  brilliant  researches  of 
Priestly  added  much  to  chemical  knowledge,  but,  above 
all,  he  will  ever  be  remembered  for  his  discovery,  in 
1774,  of  oxygen  gas.  Nitrogen  had  already,  in  1772, 
been  obtained  by  Rutherford,  and  immediately  after 
his  own  discovery  of  oxygen,  Priestly  arrived  at  the 
right  conclusion  in  regard  to  the  nature  of  air,  i.e.,  that 
it  is  a  mixture  of  two  gases. 

Priestly  failed,  however,  to  find  a  true  explanation 
for  combustion,  doubtless,  because  he  clung  so  tena- 
ciously to  the  theory  of  phlogiston.  He,  too,  as  well 
as  Cavendish,  never,  to  his  dying  day,  was  convinced 
of  the  absurdity  of  a  belief  in  phlogiston. 

1  Joseph  Priestly  lived  1733-1804. 

3  Karl  Wilhelm  Scheele  lived  1742-1786. 


SCHEELE.  151 

It  is  interesting  to  note  Priestly's  ideas  of  original 
investigations,  differing,  as  they  do,  so  much  from 
those  now  held.  It  has  been  said  that  "he  believed 
that  all  discoveries  are  made  by  chance  and  he  com- 
pares the  investigation  of  nature  to  a  hound,  wildly 
running  after,  and  here  and  there  chancmg  on  game 
[or  as  James  Watt  called  it,  his  random  haphazarding], 
whilst  we  would  rather  be  disposed  to  compare  the 
man  of  science  to  the  sportsman,  who  having,  after 
persistent  effort  laid  out  a  distinct  plan  of  operations, 
makes  reasonably  sure  of  his  quarry."  l 

Scheele,  however,  formed  a  striking  contrast  to 
Priestly  in  his  methods  of  investigation,  for  of  Scheele 
it  has  been  said  truly,  "  his  discoveries  were  not  made 
at  haphazard  but  were  the  outcome  of  experiment  care- 
fully planned."  Though  living  in- a  country  where  he 
had  little  scientific  companionship  and  where  it  was  hard 
to  obtain  apparatus  and  materials  for  his  researches,  and 
though  he  himself  was  often  hard-pressed  by  poverty, 
Scheele  contributed  an  immense  amount  to  the  rapidly 
increasing  store  of  chemical  knowledge.  As  examples, 
from  the  long  list  of  his  works,  may  be  selected :  his 
devising  new  ways  for  preparing  medical  chemicals ; 
his  qualitative  analyses  of  many  new  minerals,  from  one 
of  which  he  got  molybdic  acid ;  his  proof  that  plumbago 
is  chiefly  carbon ;  his  discovery  of  an  acid  [now  called 
lactic]  in  sour  milk ;  his  preparation  of  mucic  acid  from 
milk  sugar ;  his  discovery  of  glycerine  and  many  acids 
in  the  vegetable  kingdom,  e.g.,  tartaric,  citric,  malic, 
oxalic,  and  gallic;  his  discovery,  in  an  investigation 

1  Koscoe  and  Schorlemmer,  Treatise  on  Chemistry,  vol.  I. 


152  PNEUMATIC   PERIOD. 

of  Prussian  blue,  of  hydrocyanic  acid,  whose  properties 
he  described,  speaking  of  its  smell  and  taste,  but  totally 
ignorant  of  its  frightfully  poisonous  nature ;  his  prep- 
aration of  a  beautiful  bright  green  coloring  matter, 
ever  since  called  Scheele's  green l ;  and,  above  all,  his 
extended  w*ork  on  the  black  oxide  of  manganese. 
Scheele  died  at  the  early  age  of  forty-four,  but  the 
number  of  discoveries  in  that  short  life  is,  perhaps, 
unprecedented.  A  remarkable  power  of  observation, 
an  extreme  diligence,  and  an  ability  to  plan  experi- 
ments which  should  bear  directly  on  the  question  in 
hand  and  give  decisive  results  in  the  quickest  and 
simplest  way,  have  given  Scheele  a  high  rank  among 
chemists  of  all  lands  and  all  times.  He  constantly 
sought  the  truth  by  all  the  means  at  his  command ; 
he  was  never  content  to  leave  anything  in  doubt  which 
could  possibly  be  proved  by  experiment;  nor  was  he 
ever  satisfied  to  let  his  investigation  of  any  compound 
rest  until  he  could  both  take  it  to  pieces  and  put  it 
together  again.  To  attain  his  ends,  he  begrudged  no 
amount  of  labor  on  his  own  part.2  In  his  investiga- 
tion of  the  black  oxide  of  manganese,  then  called 
magnesia  nigra,  he  discovered  no  less  than  four  sub- 
stances, baryta,  manganese,  chlorine,  and  oxygen.  It 
was  a  strange  coincidence  that  Scheele  in  Sweden, 

1  Prepared  by  adding  sodium  arsenite  to  a  copper  solution,  copper 
arsenite  being  thrown  down  as  a  grass  green  precipitate.     This  sub- 
stance has  been  used  largely  for  a  paint,  but  as  its  poisonous  character 
is  now  well  known  it  is  being  superseded  by  other,  e.g.,  aniline, 
greens. 

2  It  is  supposed  that  Scheele's  constant  application  to  his  work, 
particularly  at  night,  brought  on  a  sickness  which,  aggravated  per- 
haps by  actual  want,  caused  his  early  death, 


LAVOISIER.  158 

independently  of  Priestly  in  England,  should  dis- 
cover such  an  important  substance  as  oxygen  in  the 
very  same  year,  1774,  and  also  arrive  at  the  same 
conclusion  in  regard  to  the  composition  of  the  air. 
They  concluded,  as  Priestly  stated  it,  that  "the  air 
must  be  made  up  of  elastic  fluids  of  two  kinds." 
Both  Scheele  and  Priestly  first  prepared  oxygen  from 
red  oxide  of  mercury. 

But  neither  Scheele  nor  Priestly  applied  his  knowl- 
edge of  the  nature  of  air  to  an  interpretation  of  the 
phenomena  of  combustion,  a  true  explanation  of  which 
was  reserved  for  the  French  physicist  and  chemist, 
Lavoisier.1  Though  the  discovery  was  not  long  delayed, 
an  important  intermediate  step  had  to  be  taken.  Cav- 
endish isolated  hydrogen  and  called  it  "inflammable 
air."  Soon  after  the  discovery  of  oxygen,  he  found 
that  a  mixture  of  hydrogen  and  oxygen  when  exploded 
produce  water.  This  was  a  very  important  discovery, 
for  hitherto  water  had  been  considered  a  simple  sub- 
stance* As  early  as  1770,  Lavoisier  had  conducted  an 
elaborate  experiment  which  disproved  the  theory  that 
by  long  boiling  water  could  be  converted  into  earth. 
He  boiled  water  for  many  days  in  a  closed  vessel, 
having  first  weighed  the  vessel  and  the  water.  At 
the  end  of  the  boiling  he  did  find  a  considerable 
amount  of  earthy  matter  in  the  water,  but,  as  the 
gain  in  weight  of  the  water  corresponded  to  the  loss 
in  weight  of  the  vessel,  he  rightly  concluded  that  the 
water  had  dissolved  some  of  the  earthy  matter  of  the 
vessel. 

1  Born  in  1743,  impeached  under  the  Reign  of  Terror  at  the  time  of 
the  French  Revolution,  Lavoisier  was  executed  in  May,  1794. 


154  PNEUMATIC   PERIOD. 

Lavoisier  was  a  physicist,  and  as  such  had  an  extreme 
love  for  the  nicety  of  physical  measurements.  It  was 
his  application  of  the  balance  to  a  study  of  chemical 
changes  that  enabled  him  to  use  the  discoveries  of 
Priestly,  Scheele,  Cavendish,  and  others  in  arriving 
at  the  true  explanation  of  the  process  of  combustion, 
and  thus  changing  completely  the  prevailing  ideas  in 
regard  to  the  nature  of  combustion,  as  well  as  those 
about  the  respiration  of  animals. 

It  was  in  1770  that  Lavoisier  published  an  account 
of  his  celebrated  experiment  on  the  change  of  water 
into  earth.  Soon  after  this,  he  turned  his  attention 
to  the  study  of  combustion  phenomena,  particularly 
those  in  which  a  metal  on  being  heated  in  contact 
with  the  air  forms  a  non-metallic  substance.  For  this 
work  he  made  use  of  a  delicate  balance,  weighing  the 
substances  to  be  burned  and  weighing  the  products 
of  combustion.  At  first,  Lavoisier  was  a  believer  in 
phlogiston,  but  he  soon  threw  over  this  belief.  Though 
the  phlogistonists  eagerly  grasped  at  the  newly-dis- 
covered hydrogen  and  attempted  to  identify  this  as 
their  long  sought  for  phlogiston,  and  though  it  did 
seem  as  though  hydrogen  might  be  phlogiston,  inas- 
much as  when  hydrogen  is  added  to  the  oxide  of  a 
metal,  the  metal  appears  again;  still  there  was  one 
important  fact  which  no  theory  of  phlogiston  had 
been  able  to  explain,  i.e.,  the  production  of  quick- 
silver when  the  red  oxide  of  mercury  is  heated  apart 
from  hydrogen,  charcoal,  or  any  other  substance. 

As  early  as  1772,  Lavoisier  felt  so  sure  that  he  was 
on  the  track  of  something  new  in  regard  to  combus- 


THEORY   OF    COMBUSTION.  155 

tion,  that  he  sent  to  the  French  Academy  a  sealed 
note  containing  a  description  of  his  work  up  to  that 
time.  In  this  note  he  stated  that  when  sulphur, 
phosphorus,  and  some  of  the  metals  are  burned,  the 
increase  in  weight  is  caused  by  the  absorption  of  air. 
A  hundred  years  before  this,  Mayow1  had  arrived  at 
the  conclusion  that  our  atmosphere  [and  nitre  also] 
contains  a  substance  which  is  able  to  unite  with  metals 
when  they  are  heated,  and  is  also  used  by  the  lungs 
when  we  breathe,  changing  the  spent  blood  into  the 
fresh  arterial.  This  substance,  contained  in  the  air 
and  in  nitre,  he  called  spiritus  igno-aereus  or  nitro 
aereus.  Had  Mayow  lived,  it  is  possible  that  he, 
instead  of  Lavoisier,  might  have  made  the  great  gen- 
eralization which  fell  to  the  lot  of  the  latter. 

In  his  note  to  the  French  Academy,  Lavoisier  stated 
that  when  litharge  [an  oxide  of  lead]  is  heated  with 
coal  in  a  closed  vessel  a  great  volume  of  air  is  pro- 
duced. It  was  not  long,  however,  before  he  himself 
saw  that  it  was  not  air,  but  another  gas  which  was 
produced  in  this  reduction  of  litharge.  As  we  have 
seen,  the  discovery  of  oxygen  came  in  1774.  Lavoisier, 
unhampered  by  any  desire  to  perpetuate  the  phlogiston 
theory,  saw  at  once  that  the  discovery  of  oxygen  gave 
the  key  to  the  explanation  of  the  most  important  chem- 
ical question  of  the  times.  He  saw  that,  if  you  assume 
that  in  combustion  this  gas  combines  with  the  metals, 
charcoal,  sulphur,  etc.,  you  can  explain  the  increase  in 
weight  as  well  as  all  other  changes  without  having  to 
resort  to  any  such  absurdity  as  a  substance  with  a 

1  John  Mayow,  born  1645,  died  in  1679  at  the  early  age  of  34. 


156  PNETTMATIC   PERIOD. 

negative  weight.  In  1775  he  published  his  opinions 
in  regard  to  the  action  of  oxygen;  in  1776  he  showed 
that  when  the  diamond  is  burned  oxide  of  carbon  is 
produced ;  and  in  1777  he  proved  the  amount  of 
oxygen,  by  volume,  in  the  air  by  burning  phosphorus 
in  a  closed  vessel,  and  noting  that  one  fifth  of  the  air 
had  disappeared  after  the  burning. 

Briefly  stated,  Lavoisier's  oxidation  theory  was  that 
substances  burn  only  in  extremely  pure  air ;  that  when 
a  substance  is  burned,  for  the  increase  in  weight  there 
is  a  corresponding  decrease  in  the  weight  of  the  air; 
also,  that  the  substance  burned  is  changed  into  a  sub- 
stance which  is  generally  an  acid,  though  the  metals 
yield  substances  which  are  not  acid.  From  this  it  will 
be  seen  that  Lavoisier  thought  the  acids  contained 
oxygen.  He  tried  to  prove  that  oxygen  itself  was  an 
acidifying  principle,  believing,  for  instance,  that  sul- 
phuric aeid  consisted  of  sulphur  and  oxygen,  and  phos- 
phoric acid  of  phosphorus  and  oxygen.  Even  hydrochlo- 
ric acid  he  thought  must  contain  oxygen,  and,  assuming 
that  when  hydrogen  is  burned  an  acid  must  result,  he 
attempted  to  find  the  acid.  In  1783,  however,  Caven- 
dish discovered  that  water  is  the  product  of  the  com- 
bustion of  hydrogen.  Then  Lavoisier  made  use  of  this 
discovery  of  Cavendish's  in  explaining  correctly  the 
manner  in  which  hydrogen  is  produced  from  water  by 
red-hot  iron ;  the  cause  for  the  appearance  of  water 
when  oxides  are  reduced  by  hydrogen ;  and  the  produc- 
tion of  hydrogen  from  acids  by  adding  them  to  metals. 

These  important  explanations  led  to  such  great 
reforms  in  chemistry  that  the  admirers  of  Lavoisier 


CONSERVATION   OF   MASS.  157 

have  sometimes  claimed  that  he  was  the  founder  of 
scientific  chemistry.  That  chemistry  was  a  science 
long  before  this,  however,  we  have  already  seen. 

To  Lavoisier  we  must  give  the  credit  of  first  dis- 
covering a  law  of  general  application  in  chemistry. 
Never  before  his  time  do  we  find  a  man  thoroughly 
impressed  with  the  idea  that  no  matter  is  lost  how- 
ever great  the  change  in  which  it  is  involved.  He, 
however,  seems  to  have  had  this  belief  constantly  fixed 
in  mind,  and  as  constantly  to  have  directed  his  ex- 
periments toward  proving  that  the  sum  of  the  weights 
of  the  factors,  in  a  chemical  change,  is  exactly  equal  to 
the  sum  of  the  weights  of  the  products.  This  great 
generalization  is  called  The  L.aAv  of  Conservation  of 
Mass,  or  of  the  Indestructibility  of  Matter. 


Experiment  17. 
Conservation  of  Mass. 

The  Law.  The  sum  of  the  weights  of  the  products 
of  a  chemical  change  is  exactly  equal  to  the  sum  of  the 
weights  of  the  factors. 

A.     The  Combustion  Products  of  a  Candle. 

Take  a  piece  of  fine  iron  gauze.  Cut  from  it  a 
circular  piece  about  three  and  one  half  inches  in 
diameter.  Take  a  square  foot  of  the  same  gauze.1 
With  the  square  foot  make  a  cylinder  around  the 

i  One  piece  of  gauze  will  do  for  a  large  class  of  students, 


158  PNEUMATIC    PERIOD. 

circular  piece,  so  that  the  circular  piece  shall  form 
a  shelf  half  way  down  the  cylinder  and  divide  the 
volume  of  the  cylinder  in  two  equal  portions.  The 
cylinder  may  be  kept  in  place  around  the  disk  by 
being  wound  with  wire. 

Place  a  five-inch  piece  of  paraffine  candle  on  one 
pan  of  a  platform  balance.  Set  the  cylinder  over  the 
candle.  In  the  upper  compartment  put  150-200g  of 
hydroxide  of  sodium1  in  stick  form.  Balance  the 
apparatus  with  any  convenient  tare.  Light  the  candle 
and  let  its  flame  pass  up  among  the  sticks  of  hydroxide. 
At  the  end  of  five  minutes  note  the  gain  in  weight. 
Put  out  the  flame  and  wait  five  minutes  more.  Note 
that  during  the  second  five  minutes  there  is  a  slight 
gain  in  weight,  due  to  the  absorption  of  moisture  from 
the  air  by  the  deliquescent  hydroxide  of  sodium.  This 
gain,  however,  is  only  a  small  fraction  of  the  amount 
gained  when  the  candle  was  burning.  Therefore, 
though  the  candle  was  gradually  disappearing,  the 
substance  of  the  candle  was  not  annihilated.  What 
have  we  already  found,  by  means  of  lime  water,  to 
be  one  of  the  products  when  a  candle  burns  in  air? 
Hold  a  clean,  cold,  and  dry  tt  directly  over  the  flame  of 
a  candle,  but  not  near  enough  to  the  flame  to  touch  it. 
What  is  a  second  product  of  the  burning?  Analysis 
would  show  that  the  candle  is  composed  of  a  substance 
—  paraffine —  which  is  itself  composed  of  carbon  and 
hydrogen  only.  What  happens  to  hydroxide  of  sodium 

1  As  soon  as  one  student  has  used  this  hydroxide  of  sodium  it  should 
be  put  in  a  bottle,  for,  if  kept  away  from  the  air,  it  will  serve  for  eight 
or  ten  students.  The  circular  shelf  of  gauze,  however,  should  be 
washed  after  every  trial. 


CONSERVATION   OF   MASS.  159 

when  in  contact  with  dioxide  of  carbon,  when  in  contact 
with  water?  Why  was  there  an  actual  gain  in  weight 
in  this  experiment? 

B.     The  Weight  of  the  Products  is  Equal  to  the  Weight  of 
the  Factors. 

Take,  of  thoroughly  dry  nitrate  of  barium,  exactly 
10g  and,  of  thoroughly  dry  sulphate  of  potassium, 
exactly  7g.  Dissolve  each  substance  in  a  separate 
beaker  containing  about  100CC  of  water.  Bring  both 
solutions  just  to  a  boil.  Add  one  to  the  other,  washing 
the  last  drops  from  the  beaker  by  means  of  the  wash- 
bottle.  Note  the  metathesis.  The  barium  changes 
place  with  the  potassium,  and  there  results  sulphate 
of  barium  and  nitrate  of  potassium.  Let  the  sulphate 
settle.  Have  ready  a  weighed  filter  paper  in  a  3-inch 
funnel.  Decant  the  clear  liquid,  through  the  filter, 
into  a  good-sized  weighed  beaker,  or  evaporating  dish. 
Transfer  the  precipitate  to  the  filter,  washing  out  every 
bit  by  means  of  the  wash-bottle.  Do  not  lose  any  pre- 
cipitate, and  save  all  the  wash  water.  Collect  all  the 
filtrate,  and  evaporate,  cautiously,  to  dryness.  Get 
the  weight  of  the  residue.  Also  dry  the  precipitate 
and  get  its  weight.  Compare  the  sum  of  the  weights 
of  the  two  products  with  the  sum  of  the  weights  of 
the  two  factors. 

For  Review.  What  is  the  meaning  of  pneumatic? 
To  what  period  of  chemistry  is  it  applied  ?  What  did 
Van  Helmont  contribute  to  this  period?  What  did 
Boyle  contribute  to  our  knowledge  of  gases?  What 


160  PNEUMATIC    PERIOD. 

did  Black  contribute?  State  the  law  of  Dalton  [or 
Charles].  What  is  the  absolute  scale  of  temperature? 
When  did  Cavendish  live  ?  What  do  we  owe  to  him  ? 
What  is  the  distinction  between  density  and  specific 
gravity?  How  may  gases  be  distinguished  from  one 
another  ?  Who  determined  the  composition  of  the 
atmosphere  ?  When  was  nitrogen  discovered  ?  When 
was  oxygen  discovered,  and  by  whom?  What  is 
Scheele's  green?  What  enabled  Scheele  to  accom- 
plish so  much  in  so  few  years  ?  When,  and  by  whom, 
was  the  composition  of  water  proved?  Who  was 
Lavoisier?  What  did  Lavoisier  apply  in  chemistry? 
State  Lavoisier's  theory  of  combustion.  What  was 
Lavoisier's  theory  in  regard  to  acids  ?  State  the  first 
great  law  of  chemistry.  What  is  this  law  called? 
Give  an  illustration  of  this  law. 


THE  ATOMIC  THEORY  PERIOD.        161 

CHAPTER   VIII. 

THE   MODERN,    OR   ATOMIC   THEORY,   PERIOD. 

§  1.  John  Dalton1  proposed  the  most  celebrated 
theory  chemistry  has  ever  had  —  a  theory  which  has 
been  a  safe  guide  for  its  followers  ever  since.  Soon 
after  Lavoisier  established  the  law  of  conservation  of 
mass,  two  other  fundamental  laws  of  chemistry  were 
discovered,  and  it  was  while  pondering  over  these  last 
two  laws  that  Dalton  formed  an  hypothesis  in  regard 
to  the  constitution  of  matter  which  soon  developed 
into  his  famous  Atomic  Theory. 

During  the  last  decade  of  the  eighteenth  century, 
Richter,2  a  German  chemist,  investigated  the  neutral- 
ization of  acids  with  alkalies,  and  stated  that  when 
several  portions,  all  equal  in  weight,  of  an  acid  are 
taken  and  neutralized,  each  with  a  different  alkali, 
the  amounts  of  the  alkalies  are  equivalent.  He  also 
believed  that  the  composition  of  a  substance  is  con- 
stant, e.g.,  that  whenever  nitre  is  made  by  neutralizing 
nitric  acid  with  hydroxide  of  potassium  the  amount 
of  potassium  in  a  given  weight  of  the  nitre  is  always 
the  same,  and  that  when  zinc  sulphate  is  formed  by 
the  action  of  zinc  on  sulphuric  acid  the  percentage  of 
zinc  in  the  resulting  sulphate  does  not  vary  whether 
a  large  or  a  small  amount  of  acid  has  been  used., 

There  was   an   eminent   French   chemist,  however, 

1  Lived,  1766-1844,  in  England. 

2  Jeremias  Benjamin  Richter,  born  in  1762,  died  in  1807,  worked  in 
Breslau  and  at  Berlin. 


162  THE   MODERN   PERIOD. 

Berthollet,1  who,  in  the  first  decade  of  the  nineteenth 
century,  advanced  ideas  very  much  opposed  to  those 
of  Richter.  Berthollet  did  not  believe  that  compounds 
possess  a  fixed  composition.  He  maintained  that  when 
a  compound  is  formed  from  two  simple  substances,  the 
amount  of  either  constituent  in  the  resulting  compound 
varies  according  to  the  quantity  of  that  factor  at  hand, 
e.g.,  that  if  an  acid  be  treated  with  a  large  amount  of  a 
metallic  hydroxide,  the  resulting  salt  will  contain  more 
metal  than  it  would  had  a  smaller  proportion  of  the 
hydroxide  been  used,  and  vice  versa. 

On  account  of  the  above  assumption,  Berthollet 
soon  became  involved  in  a  dispute,  which  lasted  for 
eight  years,  with  another  chemist,  Proust.2  Proust 
had  already  shown  that  a  number  of  substances  never 
vary  in  composition.  He  now  undertook  to  prove 
the  falsity  of  Berthollet's  assumption,  and  in  the  end 
succeeded  in  showing  that  his  opponent  had  often 
analyzed  mixtures,  instead  of  true  chemical  com- 
pounds. Very  likely  Berthollet  himself  had  been  led 
astray  by  the  now  well-known  fact  that  some  sub- 
stances form  with  others  a  series  of  compounds,  e.g., 
sulphur,  we  have  found,  forms  with  oxygen  sulphurous 
oxide  and  sulphuric  oxide,  carbon  also,  we  saw,  forms 
two  oxides,  and  nitrogen  forms  not  less  than  five. 
While  Berthollet  believed  that  metals  form  oxides 
with  gradually  and  indefinitely  increasing  amounts  of 
oxygen,  Proust  proved  that  the  formation  goes  on  in 
jumps,  i.e.,  that  a  given  substance,  capable  of  forming 
two  oxides,  after  it  has  taken  up  a  given  amount  of 

1  Claude  Louis  Berthollet,  born  in  1748,  died  1822, 

2  Born  1755,  died  1826. 


DEFINITE    PROPORTIONS    BY    WEIGHT.  163 

oxygen  and  formed  the  first  oxide,  will  not,  as  the 
conditions  are  varied,  take  up  a  little  more  and  then 
a  little  more  oxygen  till  complete  saturation  is  reached, 
but  will  jump  at  once  from  the  first  proportion  to  the 
last.  As  the  result  of  this  famous  controversy  a  second 
great  law  of  chemistry  became  established.  This  law 
may  be  stated  thus.  Every  distinct  chemical  compound 
has  a  fixed  and  unalterable  composition.  This  is  called 
The  Law  of  Definite  Proportions  by  Weight. 


Experiment  18. 

Law  of  Definite  Proportions  by  Weight. 

Weigh  out  exactly  10  grams  of  sal  soda.  The  sal 
soda  should  be  in  good  clear  crystals,  not  effloresced. 
Put  the  sal  soda  in  a  beaker  tall  enough  to  avoid  sub- 
sequent spattering  out.  Dissolve  in  40-50CC  of  water. 
Add  hydrochloric  acid  solution  till  no  more  effervescence 
takes  place.  Transfer  the  liquid  to  a  weighed  evapo- 
rating dish,  washing  the  last  traces  from  the  beaker 
into  the  dish  with  pure  water  from  the  wash-bottle. 
Evaporate  to  dryness,  avoiding  all  spattering.  Get 
the  weight  of  the  residue. 

Again  take  exactly  10  grams  of  sal  soda,  treat  with 
hydrochloric  acid  as  before,  but  when  the  effervescence 
has  ceased  add  a  considerable  excess  of  hydrochloric 
acid.  Evaporate,  and  weigh.  Compare  the  weight 
with  the  first.  Has  there  been,  in  the  second  case, 
a  taking  up  of  an  excess  of  the  acid  principle? 


164  THE  MODEBN  PERIOD. 

§  2.     QUANTITATIVE  ANALYSIS. 

The  branch  of  chemistry  called  Quantitative  Analysis 
is  based  upon  the  law  of  definite  proportions  by  weight. 
In  Qualitative  Analysis,  the  chemist  has  to  determine 
what  substances  are  present  in  the  body  to  be  analyzed. 
In  Quantitative  Analysis,  he  determines  how  much  of 
a  substance,  known  to  be  present,  is  present.  As  in 
Qualitative  Analysis,  so  in  Quantitative,  the  substance 
looked  for  can  sometimes  be  isolated,  e.g.,  when  we 
desire  to  know  the  amount  of  mercury  in  a  given 
weight  of  the  red  oxide  of  mercury,  we  can  heat  the 
substance  and  weigh  the  resulting  mercury;  or  if  we 
wish  to  know  the  amount  of  iron  in  iron  oxide  we 
can  pass  hydrogen  over  the  hot  oxide,  and  after  the 
hydrogen  has  carried  off  all  the  oxygen  we  can  weigh 
the  remaining  iron ;  or  when  we  have  passed  the  electric 
current  through  a  compound  in  solution,  often  one  of 
the  constituents  is  deposited,  or  driven  off  as  a  gas, 
and  this  we  can  collect  and  weigh.  But  in  a  vast 
number  of  cases,  when  quantitative  analyses  are  called 
for,  no  such  isolation  can  be  made.  In  these  cases  cer- 
tain chemical  changes  are  brought  about  which  convert 
the  whole  of  the  substance  looked  for  into  some  sub- 
stance whose  percentage  composition  is  known,  or  can  be 
found,  and  whose  weight  can  be  determined  accurately. 
For  instance,  we  desire  to  know  the  amount  of  chlorine 
in  a  gram  of  the  salt  just  made  in  Ex.  18.  It  would  be 
very  hard  to  isolate  this  chlorine  from  its  sodium,  and 
next  to  impossible  to  weigh  it  accurately  if  isolated. 
But  we  can  easily  combine  the  chlorine  with  silver  [while 


QUANTITATIVE   ANALYSIS.  165 

at  the  same  time  we  combine  the  sodium  with  nitrogen 
and  oxygen  to  form  nitrate  of  sodium]  and  thus  convert 
the  chlorine  all  into  silver  chloride,  which  we  can 
weigh.  If,  now,  we  determine  the  percentage  of  chlo- 
rine in  silver  chloride,  as  we  can  do  in  a  simple  manner, 
we  can,  by  arithmetic,  calculate  the  weight  of  chlorine 
in  the  silver  chloride  that  was  formed  from  our  original 
gram  of  salt,  for  the  law  of  definite  proportions  by 
weight  declares  that  every  compound  has  a  fixed  and 
unalterable  composition,  hence  the  percentage  composi- 
tion of  silver  chloride  made  in  one  way  must  be  the 
same  as  that  of  silver  chloride  made  in  any  other  way. 
Knowing  the  weight  of  chlorine  in  the  silver  chloride 
made  from  our  salt,  we  know  the  weight  of  chlorine  in 
the  salt  because  all  the  chlorine  of  the  salt  went  into 
this  silver  chloride. 


Experiment  19. 

Analysis  of  Table  Salt. 

What  simple  substances  have  we  already  proved  to 
be  in  table  salt  ?  How  did  we  prove  this  ? 

Have  ready  about  5g  of  c.p.  sodium  chloride.  To 
make  sure  that  the  salt  is  thoroughly  dry,  pulverize  it, 
put  it  in  a  porcelain  evaporating  dish  and  heat  for  about 
five  minutes  over  the  Bunsen  burner  flame.  When  cool, 
weigh  out,  on  the  small  balances,  exactly  lg  of  the  salt. 
Put  the  salt  in  a  medium-sized  beaker,  add  about  30CC  of 
distilled  water,  and  warm  till  solution  takes  place.  Then 
weigh  out,  and  place  in  a  similar  beaker,  5.0g  of  nitrate 


166  THE    MODERN   PERIOD. 

of  silver.  Dissolve  the  nitrate  of  silver  also  in  about 
30CC  of  distilled  water.  Heat  both  solutions  till  you 
just  cannot  bear  your  hand  on  the  sides  of  the  beakers, 
then,  using  a  glass  rod  to  direct  the  stream,  pour,  care- 
fully, with  constant  stirring,  the  salt  solution  into  the 
nitrate  solution.  With  a  stream  of  water  from  the 
wash-bottle,  wash  out  into  the  main  liquid  the  last 
traces  of  the  salt  solution.  Protect  the  contents  of 
the  beaker  from  the  action  of  sunlight.  Continue  to 
heat,  gently,  till  the  precipitate  has  settled.  Have 
ready,  in  a  funnel,  a  well  dried  and  weighed  filter. 
Decant  the  clear  liquid,  down  a  rod,  through  the  filter. 
Transfer  all  the  precipitate  to  the  filter.  In  order  to 
get  out  the  last  particles  make  use  of  the  glass  rod1  and 
a  stream  from  the  wash-bottle.  Wash  the  precipitate 
well  with  distilled  water,  and  dry2  it  on  the  paper. 
Dry  to  constant  weight,  but  do  not  burn  the  paper. 
Get  the  weight  of  the  silver  chloride  formed. 

In  order  to  find  the  amount  of  chlorine,  we  must 
know  what  per  cent  of  chlorine  there  is  in  silver  chlo- 
ride itself.  Determine  this  as  follows: 

Weigh  out,  on  the  small  balances,  exactly  lg  of  pure 
silver.  Place  the  silver  in  a  small  beaker,  and  add 
about  2CC  of  nitric  acid  diluted  with  two  or  three  times 
its  volume  of  water.  Heat,  gently,  to  produce  rapid 
solution.  When  the  silver  is  all  changed  to  the  soluble 
nitrate,  add  about  25CC  of  distilled  water.  In  a  second 
beaker  dissolve  in  about  30CC  of  distilled  water,  at  least 
2g  of  c.p.  chloride  of  sodium.  Heat  each  solution;  mix; 

1  For  this  work  it  is  well  to  have  on  the  end  of  the  glass  rod  a  piece 
of  tightly  fitting  rubber  tube  about  lcm  long. 

2  See  Appendix  M, 


ANALYSIS  OF  TABLE  SALT.          167 

let  settle ;  filter ;  wash,  dry,  and  weigh  the  precipitate, 
exactly  as  in  the  previous  part  of  the  experiment. 
The  silver  has  taken  to  itself  chlorine  from  the  chlo- 
ride of  sodium.  The  precipitate  consists  of  silver 
chloride. 

The  amount  that  this  chloride  of  silver  weighs  in 
excess  of  the  lg  of  silver  represents  the  amount  of 
chlorine  the  silver  has  taken,  and  from  these  figures 
the  per  cent  of  chlorine  in  chloride  of  silver  may  be 
found. 

Now  calculate  the  amount  of  chlorine  in  the  lg  of 
chloride  of  sodium,  and  also  the  amount  of  sodium. 
Let  the  final  results  be  stated  in  parts  per  100,  i.e., 
in  percentages.  A  good  worker  should  come  within 
\°jo  of  the  true  amount  of  chlorine.1 

For  Review.  —  §§1  and  2.  Who  proposed  the  cele- 
brated atomic  theory  ?  What  was  it  that  Kichter  noted 
in  the  last  decade  of  the  eighteenth  century?  What 
did  Richter  believe  in  regard  to  the  composition  of 
substances?  What  did  Berthollet  maintain?  What 
did  Proust  prove  ?  How,  probably,  did  it  happen  that 
Berthollet  was  led  astray  ?  State  the  second  great  law 
of  chemistry.  What  is  this  law  called?  State  the 
results  of  an  experiment  that  illustrate  this  law.  What 
is  the  object  of  Quantitative  Analysis  ?  How  does 
Quantitative  Analysis  depend  on  the  second  great  law 
of  chemistry?  Describe,  briefly,  an  experiment  that 
shows  how  quantitative  determinations  are  usually 
made  in  chemistry. 

1  With  the  best  of  balances  a  good  worker  should  come  within  0.1% 
of  the  true  amount. 


168  THE   MODERN    PERIOD. 


§  3.     MULTIPLE  PROPORTIONS. 

Had  Proust,  in  his  examination  of  those  cases  in 
which  a  given  substance  forms  two  or  more  oxides, 
thought  to  start  with  some  definite  amount  of  the  one 
substance  and  calculate  ratios  between  the  varying 
amounts  of  the  second  which  unite  with  the  first,  he 
would  probably  have  been  gthe  discoverer  of  the  third 
great  law  of  chemistry.  For  instance,  10g  of  carbon 
produce  either  23. 3g  of  the  combustible  oxide  or  36. 6g 
of  the  non-combustible.  Now  deducting,  in  each  case, 
the  10g  of  carbon,  we  find  that  in  the  first  case  there  has 
been  a  taking  on  of  13.3g  of  oxygen  and  in  the  second 
26. 6g  or  just  twice  as  much,  i.e.,  the  ratio  between  the 
two  amounts  of  oxygen,  when  the  amount  of  carbon 
remains  fixed,  is  a  very  simple  one  — 1:2.  But  it  does 
not  seem  ever  to  have  occurred  to  Proust  to  make  such 
a  comparison.  Dalton,  however,  saw  that  it  might  be 
done.  It  was  when  examining  two  gaseous  hydrogen 
compounds  of  carbon  —  olefiant  gas  and  marsh  gas 1  - 
that  Dalton  did  this.  In  100g  of  olefiant  gas  there  are 
85. 7g  of  carbon  and  14. 3g  of  hydrogen,  while  in  100g 
of  marsh  gas  there  are  75. Og  of  carbon  and  25. Og  of  hy- 
drogen. Now,  calling  the  amount  of  hydrogen,  in  each 
case,  any  fixed  number,  as  10,  and  making  proportions, 

14.3  :  85.7  : :  10  :  x  25  :  75  : :  10  :  x 

x  =  GO  x  =  30 

30  :  60  : :  1  :  x 


1  The  "fire-damp"  of  the  mines.  The  oxide  of  carbon  which 
results  from  the  explosion  of  this  gas  mixed  with  air  is  called  the 
"  choke-damp." 


MULTIPLE   PROPORTIONS.  169 

we  find  that  the  amount  of  carbon  in  the  first  case  is 
to  the  amount  of  carbon  in  the  second  case  as  2:1. 
Dalton  also  examined  the  two  oxides  of  carbon,  and 
found,  as  we  have  seen,  that  the  amount  of  oxygen 
in  the  one  is  to  the  amount  in  the  other  as  1:2. 
For  Dalton,  this  simplicity  of  numbers  seemed  to  have 
a  deep  meaning.  In  order  to  find  the  underlying  law, 
he  set  out  to  make  an  examination  of  other  cases,  par- 
ticularly the  formation  of  various  oxides  of  nitrogen. 
He  soon  made  the  discovery  of  the  law  of  multiple 
proportions. 

Experiment  2O. 
Multiple  Proportions. 

A.  The  Oxides  of  Sulphur. 

We  have  studied  two  oxides  of  sulphur.  In  100 
parts,  by  weight,  of  one  there  are  50  parts  of  sulphur 
and  50  parts  of  oxygen.  In  the  second,  there  are  40 
parts  of  sulphur  and  60  parts  of  oxygen.  Calculate 
the  amount  of  oxygen  there  is,  in  each  case,  if  the 
amount  of  sulphur,  in  each  case,  is  called  unity.  Then 
calculate  the  ratio  between  the  amounts  of  oxygen 
found.  Note  that  the  ratio  is  2  :  3  exactly. 

B.  The  Oxides  of  Nitrogen. 

There  are  five  oxides  of  nitrogen. 
In  the  first      the  nitrogen  rr  63.6%  and  the  oxygen  rr  36.4% 

"       "     Second      «  «  rr   46.6%      "         "  "  rr    53.4% 

"     "   third       «          "         =  36.8%    «      "         "        =  63.2% 
"     "   fourth     "          "         =  30.4%    "      «         "        =  69.6% 

"       "     fifth  «  «  rr    25.9%      "         "  «  rr    74.1% 

Find  the  simple  ratio  for  these  compounds. 


170  THE   MODERN    PERIOD. 

C.     The  Chlorides  of  Iron. 
There  are  two  chlorides  of  iron. 

The  first       has  44.1%  iron  and  55.9%  chlorine 
"     second    «    34.4%    "       "    65.6%        " 

Find  the  simple  ratio. 

The  Law  of  Multiple  Proportions  may  be  stated 
thus :  When  varying  quantities  of  one  substance  join  a 
fixed  amount  of  some  other,  the  varying  amounts  of  the 
first  bear  to  each  other  a  ratio  expressed  in  simple  numbers, 
as  1:2,  1 : 3,  2 : 3,  or  the  like. 


§  4.     D  ALTON'S  ATOMIC  THEORY. 

Dalton  did  not  rest  on  the  discovery  of  his  law  of 
multiple  proportions.  He  was  eager  for  an  explana- 
tion of  the  law  as  well  as  for  one  of  the  law  of  definite 
proportions  by  weight.  As  an  explanation  of  the  facts 
embodied  in  these  two  laws,  he  soon  proposed  one  of 
the  most  remarkable  hypotheses  that  any  branch  of 
science  has  ever  known  —  remarkable  not  only  for  the 
manner  in  which  it  explained  the  facts  known  at  its 
inception,  but  also  for  the  position  which  it  has  ever 
since  held  as  the  very  foundation  of  our  modern  chem- 
ical science.  The  essence  of  this  hypothesis  was  this : 
that  every  simple  substance  is  made  up  of  minute 
atoms,  all  alike  and  all  of  the  same  weight;  that  every 
compound  substance  is  made  up  of  minute  particles, 
all  alike,  and  each  a  collection  of  atoms  of  different 
simple  substances  grouped  in  simple  and  unalterable 


ATOMS.  171 

numerical  ratio  and  chemically  united.  The  atoms,  as 
the  name  implies,  were  considered  indivisible. 

It  has  long  been  a  favorite  discussion  among  specula- 
tive philosophers  whether  there  can  be  such  a  thing  as 
an  indivisible  particle  of  matter,  some  claiming  that 
such  a  substance  is  not  only  conceivable,  but  likely  to 
exist ;  while  others  have  said  that  every  body  we  know 
is  capable  of  division,  that  each  part  from  the  division 
is  capable  of  subdivision  and  again  these  parts  are 
divisible,  and  so  the  division  may  be  carried  on  forever 
without  arriving  at  a  true  atom,  that  is,  a  particle  ab- 
solutely indivisible.  Herbert  Spencer,1  a  philosopher 
still  living,  after  discussing  this  question,  has  concluded 
that  true  atoms  are  inconceivable.  But  the  chemist  of 
to-day  finds  it  convenient  to  assume  that  there  are  such 
particles  and,  what  is  more,  he  has  some  very  clear 
ideas  in  regard  to  them. 

However,  let  us  not  consider  the  present  conception 
of  atoms  till  we  have  traced  Dalton's  work  a  little 
farther.  Dalton  was  even  bold  enough  to  believe  that 
he  could  get  at  the  [relative]  weights  of  these  atoms,  or 
minute  particles,  which  make  up  all  matter.  He 
thought  that  this  end  could  be  attained  by  noting  the 
amount  of  one  substance  which  combines  with  a  given 
weight  of  another  in  the  formation  of  a  compound. 
For  instance,  he  made  an  experiment  and  concluded 
that  6.5g  of  oxygen  united  with  lg  of  hydrogen,2  in  the 
formation  of  water,  and,  assuming  that  the  hydrogen 
and  oxygen  united  atom  and  atom,  he  gave  to  oxygen 

1  "First  Principles." 

2  Dalton's  determination  here  was  not  accurate,  as  the  best  modern 
determinations  give  almost  8s  of  oxygen  to  Is  of  hydrogen. 


172  THE  MODERN  PERIOD. 

the  atomic  weight  of  6.5,  calling  hydrogen  unity.  But 
this  assumption,  that  one  atom  of  oxygen  joined  one 
atom  of  hydrogen,  was  not  based  on  a  knowledge  of  the 
fact,  and  was  therefore  a  mere  speculation.  We  shall 
return  to  this  point. 

Dalton  prepared  a  table  giving  numbers  for  the  atomic 
weights  of  several  different  atoms.  These  numbers  he 
frequently  altered,  and  himself  recognized  the  necessity 
for  a  most  careful  determination  in  the  case  of  every 
elementary  substance,  of  its  "  combining  number,"  that 
is,  the  number  expressing  the  proportion  by  weight  in 
which  the  substance  joins  other  substances.  Even  to 
the  present  day  these  combining  numbers  have  not  been 
definitely  fixed,  and  experiments  are  constantly  being 
carried  on  directed  to  the  accurate  determination  of  the 
combining  number  for  some  one  or  other  of  the  ele- 
mentary substances. 


§  5.     COMBINING  NUMBER. 

Let  us  determine  the  combining  number  for  an 
elementary  substance. 

Experiment  21. 
Determination  of  the  Combining-  Number  for  Zinc. 

We  know  that  zinc  will  displace  hydrogen  in  acids, 
the  zinc  entering  into  combination  where  hydrogen  was. 
If,  then,  we  should  take  a  large  weighed  piece  of  zinc 
and  let  an  acid  act  on  it  till  just  one  gram  of  hydrogen 
had  passed  off,  the  loss  in  weight  of  the  zinc  would  show 


COMBINING   NUMBER   FOB   ZINC.  173 

the  amount  of  the  latter  which  had  entered  into  com- 
bination in  the  hydrogen's  place.  The  number  express- 
ing the  number  of  grams  of  zinc  here  used  would  be 
the  combining  number  for  zinc,  if  that  for  hydrogen  is 
assumed  to  be  unity.  Hydrogen  is  such  a  light  gas 
that  it  would  require  an  experiment  on  a  large  scale  to 
obtain  a  whole  gram,  therefore  the  experiment  can  be 
made  better  as  follows. 

Take  a  100CC  flask.  Fit  it  with  a  good  one-hole  cork, 
or,  better,  a  rubber  stopper.  Have  a  delivery  tube 
reaching  to  the  pneumatic  trough.  Put  in  the  flask 
10CC  of  hydrochloric  acid  solution,  and  20CC  of  water. 
Take  some  freshly  cleaned  c.p.  zinc,  and,  using  the 
delicate  balances,  weigh  out  [accurately  to  centigrams] 
1.30g.  This  amount  will  produce  a  convenient  quantity 
of  hydrogen.  Have  ready,  inverted  and  full  of  water, 
in  the  pneumatic  trough,  a  500CC  flask  for  catching  the 
gas.  When  all  is  ready  drop  the  zinc  in  the  flask  and 
insert  the  stopper.  Let  the  action  run  to  completeness. 
Keep  all  undue  heat  away.  Why  ?  Note  whether  any 
water  has  been  sucked  back  toward  the  flask.  If  any 
has,  make  the  proper  allowance  in  measuring  the  gas 
caught.  Note  the  temperature  of  the  air  surrounding 
the  flask ;  also  read  the  barometer.  Make  the  level  of 
the  water  inside  and  outside  the  flask  the  same.  Place 
the  palm  of  the  hand  over  the  mouth  of  the  flask  and 
quickly  invert  the  flask.  From  the  graduate  add  water 
to  the  brim.  Note  how  many  cc  of  gas  the  flask  had 
collected.  One  cc  of  hydrogen  at  standard  conditions 
weighs  O.OOOO9g.  Calculate  the  iveight  of  hydrogen 
displaced.  [Note.]  If  the  lest  possible  result  is  desired, 


174  THE   MODERN   PERIOD. 

it  is  necessary  to  consider  the  effect  of  the  moisture 
that  the  hydrogen  has  taken  up  as  it  passed  through 
the  water  of  the  pneumatic  trough.  We  shall  soon 
learn  that  two  gases  can  occupy  the  same  vessel  at  the 
same  time,  and  that  the  more  gases  there  are  in  a  given 
flask  the  more  the  pressure,  —  each  gas  exerting  its  own 
pressure  against  the  confining  walls.  Although  •  the 
amount  of  water  vapor  that  any  gas,  as  hydrogen,  takes 
up  on  its  passage  through  water,  is  small  and  conse- 
quently the  amount  of  pressure  due  to  this  aqueous 
vapor  is  small,  still  it  affects  the  accuracy  of  the  result 
of  an  experiment  like  this.  When  the  hydrogen  was 
collected  it  was  not  subjected  to  the  full  pressure  of 
the  atmosphere  because  the  water  vapor  bore  part  of 
the  pressure. 

It  has  been  found  by  accurate  experimenters  that  the 
part  borne  by  the  water  vapor  is  represented 

At  10°  by  0.9  cm.  of  mercury.       At  21°  by  1.8  cm.  of  mercury. 

11°  "  1.0  "  "  "  22°  "  2.0  "  "  " 

12°  "  1.0  «  "  "  23°  "  2.1  "  "  « 

13°  "  1.1  "  "  "  24°  "  2.2  "  "  " 

14°  "  1.2  "  "  "  2o°  "  2.3  "  "  « 

15°  "  1.3  "  "  "  26°  "  2.5  «  «  « 

16°  "  1.3  "  "  "  27°  "  2.7  "  "  " 

17°  "  1.4  "  "  "  28°  "  2.8  «  «  " 

18°  "  1.5  "  "  "  29°  «  3.0  «  «  « 

19°  "  1.6  "  "  "  30°  "  3.2  "  «  « 

20°  "  1.7  "  "  "  31°  «  3.3  «  "  « 

Before  reducing  your  observed  volume  of  hydrogen 
to  volume  at  standard  conditions,  calculate  the  true 
pressure  under  which  the  hydrogen  itself  was  when 
collected.  Taking  the  weight  of  the  hydrogen  and  the 


PKOUT'S  HYPOTHESIS.  .'     175 

weight  of  the  zinc,  and  calling  the  combining  number 
for  hydrogen  unity,  make  a  proportion  and  get  the 
combining  number  for  zinc,  i.e.,  the  number  which 
represents  the  number  of  grams  of  zinc  that  take  the 
place  of  1s  of  hydrogen. 


§  6.     PBOUT'S  HYPOTHESIS. 

While  Dalton's  theory  was  in  its  infancy  an  anony- 
mous writer l  proposed  an  hypothesis,  —  that  all  the 
combining  numbers  are  whole  numbers.  He  assumed 
that  there  was  one  fundamental  substance,  —  hydro- 
gen ;  that  the  other  elements  themselves  were  com- 
posed of  various  proportions  of  hydrogen  condensed, 
and,  hence,  the  weights  of  all  other  elements  must  be 
simple  multiples  of  that  of  hydrogen.  Though  the 
hypothesis  that  all  the  weights  of  the  heavier  elements 
are  multiples  of  those  of  the  lightest  is  a  very  pleasing 
speculation,  we  can  to-day  regard  it  only  as  such.  The 
most  trustworthy  determination  of  the  combining 
weights  of  hydrogen  and  oxygen,  in  the  formation  of 
water,2  does  not  give  the  simple  ratio  1:8  but  1:7.93. 
[Dalton's  was  1:6.5;  later,  1:7.] 

For  Review.  —  §§  3,  4,  5,  and  6.  A  consideration  of 
what  facts  led  Dalton  to  the  discovery  of  the  third 
great  law  of  chemistry?  State  the  law  of  multiple 

1  The  writer  was  found  afterward  to  be  Prout. 

2  Probably  no  quantitative  determinations  in  chemistry  have  been 
carried  on  with  greater  care  and  ingenuity  than  those  directed  to 
finding  the  combining  numbers  for  oxygen  and  hydrogen. 


176  THE   MODERN   PERIOD. 

proportions.  State  the  essence  of  Dalton's  atomic 
hypothesis.  What  is  an  hypothesis?  What  is  meant 
by  the  term  atom?  State,  briefly,  the  opinions  that 
have  been  held  in  regard  to  the  divisibility  of  matter. 
How  did  Dal  ton  think  he  could  find  the  relative 
weights  of  his  atoms?  What  was  the  weak  point  of 
his  method  ?  What  is  meant  by  the  "  combining 
number"?  Describe,  briefly,  an  experiment  which 
illustrates  a  method  for  determining  a  combining 
number.  What  was  Front's  hypothesis? 


§  7.     MOLECULES. 

Dalton's  atomic  hypothesis  explained  perfectly  the 
law  of  definite  proportions  by  weight  and  the  law 
of  multiple  proportions.  For  if  the  atoms  of  every 
simple  substance  have  all  the  same  weight,  and  if  the 
particles  of  compound  substances  are  made  up  of  the 
atoms  of  different  simple  substances  grouped  in  unalter- 
able ratio,  then  it  must  follow  that  every  particle  of 
every  compound  will  have  a  fixed  and  invariable  com- 
position; while  in  the  formation  of  two  or  more  com- 
pounds, as  oxides,  from  a  fixed  quantity  of  one 
substance  and  varying  quantities  of  a  second,  the 
varying  quantities  of  the  second  must  all  be  multiples 
of  the  weight  of  the  atom  of  this  second  substance. 

That  every  particle  of  a  compound  is  made  up  of  a 
group  of  chemically-joined  atoms  of  different  kinds,  and 
that  the  weight  of  every  particle  of  a  compound  is  the 
sum  of  the  weights  of  the  atoms  of  which  it  is  composed, 
are  very  important  points.  Although,  tlve  statement 


DALTON'S  SYMBOLS.  177 

that  the  total  weight  of  every  particle  of  a  compound  is 
exactly  equal  to  the  sum  of  the  weights  of  its  constit- 
uent atoms  may  seem  self-evident  to  us,  it  was  not  so  in 
Dalton's  time,  for  it  must  be  remembered  that  heat  was 
then  considered  a  material  substance.  Let  us  also  bear 
well  in  mind  the  distinction  here  made  between  the 
particle  of  a  substance  and  an  atom.  The  smallest  par- 
ticle into  which  a  substance  can  be  divided  by  physical 
means,  i.e.,  by  any  means  except  a  chemical  change 
which  destroys  the  substance  itself,  is  generally  called 
a  molecule.  Simple  substances,  as  well  as  compounds, 
have  their  molecules.  A  molecule  of  a  simple  substance 
generally  has  more  than  one  atom  in  it,  but  never  con- 
tains atoms  of  more  than  one  kind,  whereas  a  molecule 
of  a  compound  substance  always  contains  more  than 
one  kind  of  atoms. 

To  express  his  ideas  more  clearly,  Dalton  adopted 
a  set  of  symbols. 

O  represented  an  atom  of  oxygen. 
O  "  "      "      "  hydrogen. 

•  «  "      "      "  carbon. 

O   O     "  a  particle  [molecule]  of  water. 

•  0     "  "       "  "  «  olefiant  gas. 

O  •      "  "       "  "  "  carbonous  oxide. 

O  •  O    represented  a  particle  [molecule]  of  carbonic  oxide. 


§  8.     RELATIVE  WEIGHT  OF  THE  ATOMS. 

We  have  already  said  that  Dalton  assumed  that 
hydrogen  and  oxygen,  in  the  formation  of  water,  unite 
atom  and  atom,  and  therefore  he  concluded  that  the 


178  THE   MODERN   PERIOD. 

weight  of  the  atom  of  oxygen  is  6.5  if  the  weight  of 
the  atom  of  hydrogen  is  assumed  to  be  1,  and,  in  gen- 
eral, that  the  numbers  expressing  the  atomic  weights 
are  identical  with  those  for  the  combining  numbers  of 
the  elements.  There  are,  however,  no  grounds  for  such 
an  assumption.  If  8  grams  of  oxygen  [let  us  take  the 
more  recently  determined  (round)  number,  rather  than 
Dalton's  incorrect  6.5]  join  one  gram  of  hydrogen, 
either  8,  or  some  multiple  or  submultiple  of  8,  repre- 
sents the  true  weight  of  the  atom  of  oxygen.  If  the 
two  gases  join  atom  and  atom,  the  weight  of  the  oxygen 
atom  must  be  eight  microcriths1;  but  if  two  atoms  of 
hydrogen  join  one  of  oxygen  to  form  the  molecule  of 
water,  then,  if  the  oxygen  atom  is  eight  times  as  heavy 
as  the  two  of  hydrogen,  it  must  be  sixteen  times  as 
heavy  as  one.  If  there  are  three  of  hydrogen  to  one 
of  oxygen,  the  oxygen  atom  must  weigh  twenty-four 
microcriths,  if  the  hydrogen  atom  weighs  one.  And, 
on  the  other  hand,  if  there  are  two  atoms  of  oxygen 
and  only  one  of  hydrogen,  as  the  two  of  oxygen  out- 
weigh one  of  hydrogen  eight  to  one,  then  the  atomic 
weight  of  oxygen  is  only  four. 

In  Dalton's  time  there  were  no  means  for  determining 
which  multiple  of  the  simplest  combining  number  for 
an  element  should  be  taken  as  its  true  atomic  weight. 
And  up  to  the  present  day  no  method  has  been  dis- 
covered which  will  prove  conclusively  which  multiple 
of  a  combining  number  must  be  selected.  But  from 
time  to  time  laws  have  been  discovered  which  assist  us 

1  The  unit  at  present  used  in  speaking  of  atomic  weights  is  the 
weight  of  an  atom  of  hydrogen,  and  is  called  a  microcrith,  — the  word 
with  standing  for  the  weight  of  a  liter  of  hydrogen  gas. 


DEFINITE   PROPORTIONS   BY   VOLUME.  179 

much  in  our  inquiry.  In  1808  Gay-Lussac,1  a  French 
chemist,  published  an  account  of  some  work  that  he 
and  Von  Humboldt  had  been  carrying  on  with  gases. 
Gay-Lussac's  attention  had  been  arrested  by  the  fact 
that,  when  water  is  formed  from  hydrogen  and  oxygen, 
exactly  two  volumes  of  hydrogen  to  one  of  oxygen  are 
always  required.  Examining  a  large  number  of  chem- 
ical changes  in  which  gases  are  involved,  he  discovered 
another  important  law  of  chemistry.  He  found  that 
a  simple  numerical  ratio  holds  between  the  volumes 
of  two  gases  that  unite  to  form  a  compound,  and 
also  between  the  sum  of  the  volumes  of  the  uncom- 
bined  gases  and  the  volume  of  the  product  [when  the 
product  is  in  the  gaseous  form].  In  Part  I  we  made 
a  number  of  changes  in  which  gases  were  involved. 
Note  that  one  jar  of  oxygen  gas  yielded  one  jar  of  sul- 
phurous oxide  ;  that  one  bag  of  carbon  dioxide  yielded 
one  bag  of  carbon  monoxide  ;  that  one  bag  of  carbon 
monoxide  then  yielded  one  bag  of  carbon  dioxide  ;  and 
that,  in  the  formation  of  ammonia,  five  volumes  of  hydro- 
gen and  two  volumes  of  nitric  oxide  were  required  as 
factors,  while  the  products,  steam  and  ammonia,  had 
they  been  measured,  would  have  occupied  two  volumes 
each.  In  each  of  these  cases  the  ratio  between  corre- 
sponding gaseous  volumes  may  be  expressed  by  very 
simple  whole  numbers,  thus:  1:1,  1:1,  1:1,  5:2, 
2  :  2,  and  5  +  2  =  7  :  2  +  2  =  4.  The  Law  of  Definite 
Proportions  by  Volume  may  be  stated  thus  :  In  any 
chemical  change  the  relative  volumes  of  the  gaseous  factors 
and  products  bear  to  each  other  a  simple  numerical  ratio. 

1  Born  in  1778  j  died  in  1850. 


180  THE   MODERN   PERIOD. 

Experiment  22. 
Law  of  Definite  Proportions  by  Volume. 

By  means  of  the  electric  current  decompose  water 
held  in  any  suitable  vessel.  Have  ready  two  small  tts. 
Mark1  on  one  a  volume  of  lcc,  and  on  the  other  a 
volume  of  2CC.  Fill  both  tubes  with  water.  Invert 
the  lcc  tube  over  the  pole  that  is  giving  off  oxygen, 
and  at  once  invert  the  other  over  the  hydrogen  pole. 
Note  the  ratio  of  the  volumes  of  the  two  gases  evolved 
in  any  given  time. 


§  9.     THE  MOLECULAR  THEORY. 

Soon  after  the  discovery  of  the  law  in  regard  to 
volumes,  an  Italian  physicist  proposed  an  hypothesis 
which  is  now  the  basis  of  the  celebrated  Molecular 
Theory.  In  the  year  1811,  Avogadro  made  the  sugges- 
tion that  "  equal  volumes  of  all  substances,  when  in  the 
state  of  gas,  and  under  like  conditions,  contain  the  same 
number  of  molecules."  Three  years  later  the  French 
electrician,  Ampere,  came  to  the  same  conclusion,  and 
this  hypothesis  is  now  known  either  as  that  of  Avogadr6 
or  of  Ampere.  Let  us  see  on  what  facts  this  supposi- 
tion in  regard  to  the  structure  of  gases  is  based. 

Consider  for  a  moment  the  case  of  water,  which  so 
easily  passes  from  its  common  state  of  a  liquid  to  that 

1  This  may  be  done  by  pouring  the  proper  amount  of  water  from 
a  graduate  into  the  tt  and  marking  its  height  on  the  outside  of  the 
glass. 


THE   MOLECULAR   THEORY.  181 

of  a  gas,  —  steam.  A  cubic  inch  of  water  forms  about 
a  cubic  foot  of  steam.  Now  three  suppositions  can  be 
made  in  regard  to  the  manner  in  which  the  cubic  inch 
of  water  is  able  to  occupy  the  cubic  foot  of  space  when 
the  water  has  been  converted  into  steam.  First,  it  may 
be  supposed  that  the  cubic  inch  of  water  on  being  heated 
simply  swells  out  until  it  occupies  the  whole  cubic  foot 
as  completely  in  the  gaseous  state  as  in  the  liquid.  In 
the  next  place,  it  may  be  supposed  that  the  water  is 
not  itself  an  absolutely  homogeneous  mass  of  matter, 
but  that  it  is  made  up  of  minute  particles,  each  exactly 
like  every  other,  and  that  when  the  change  of  state 
takes  place  these  particles  do  not  change  their  size  at 
all,  but  are  simply  driven  much  farther  apart.  In  the 
third  place,  it  may  be  supposed  that,  as  in  the  second, 
the  water  is  made  up  of  minute  particles,  but  that 
when  the  water  is  converted  into  steam  these  particles 
themselves  swell  out  till  they  occupy  many  times 
more  space  than  before,  and  in  this  way  the  cubic 
foot  becomes  completely  occupied.  In  both  the  first 
and  the  last  cases  there  will  be  no  vacant  space  what- 
ever in  the  cubic  foot  of  steam,  but  every  part  will 
have  its  portion  of  matter,  whereas  in  the  second  case, 
if  the  particles  do  not  change  their  original  size,  there 
will  be  vacant  spaces,  —  in  fact,  the  vacant  spaces 
will  be  vastly  larger  than  those  occupied  by  the 
particles  of  matter.  Before  we  discuss  the  relative 
probability  of  these  three  assumptions,  let  us  make  an 
experiment. 


182  THE  MODERN   PERIOD. 

Experiment  23.1 
Spaces  between  the  Molecules. 

Have  ready  a  dry  Kjeldahl  flask  fitted  with  a  two- 
hole  rubber  stopper.  Through  one  hole  pass  a  piece  of 
glass  tube.  About  a  cm  of  this  tube  should  project 
inside  the  flask,  and  about  a  cm  outside,  when  the 
stopper  is  in  position.  To  the  outer  end  of  this  tube 
fix  5  or  6cm  of  rubber  tube  carrying  two  pinch-cocks, 
one  near  each  end  of  the  rubber  tube.  Let  a  piece  of 
glass  tube  rise  from  near  the  bottom  of  the  flask,  pass 
through  the  second  hole  in  the  stopper,  and  then  be 
bent  at  a  right  angle.  By  means  of  a  bit  of  small 
rubber  tube  connect  to  this  bent  glass  tube  the  short 
arm  of  another  piece  of  glass  tube  bent  thus  :  -,  |.  Let 
the  short  arm  of  the  latter  tube,  which  is  to  serve  for 
a  pressure  gauge,  be  about  30cm  long,  and  the  long  arm 
at  least  50cm.  Have  ready  a  bath  of  boiling  water, 
which  contains  some  common  salt  [to  raise  the  tem- 
perature above  100°].  Immerse  the  Kjeldahl  flask  in 
the  bath,  but  take  care  not  to  plunge  the  flask  in  the 
hot  liquid  so  suddenly  that  the  glass  may  crack.  Clamp 
the  flask  upright,  and  also  fasten  the  gauge  tube  firmly. 
Look  at  the  flask  and  make  sure  that  it  is  dry.  Pass 
dry  air  into  the  flask.  A  good  way  to  pass  in  the  air 
is  by  means  of  the  blast-lamp  bellows.  Force  a  slow 
stream  of  air,  first  through  a  catch-bottle  of  sulphuric 
acid,  then  through  the  short  rubber  tube  into  the  flask, 
while  the  excess  of  air  escapes  through  the  gauge  tube. 
After  the  dry  air  has  been  passing  into  the  flask  for 

1  See  foot-note,  page  xxvii  of  the  Introduction. 


SPACES   BETWEEN   THE   MOLECULES.  183 

five  minutes,  close  the  lower  pinch-cock  and  disconnect 
the  catch-bottle.  Pour  mercury  into  the  gauge  tube 
till  the  short  arm  is  about  one  third  filled.  Open  the 
pinch-cock  [for  a  moment  only]  to  relieve  any  undue 
pressure,  and  mark  the  height  on  the  short  arm  to 
which  the  mercury  rises.  Note  that  the  flask  is  now 
exactly  full  of  air  [gas  No.  1].  Put  two  or  three 
drops  [only]  of  water  in  the  rubber  tube,  and  close  the 
upper  pinch-cock.  Then  open  the  lower  pinch-cock, 
and  squeeze  the  water  down  into  the  flask.  Again 
close  the  lower  pinch-cock.  Note  that  the  water  evapo- 
rates and  forms  steam  [gas  No.  2],  Note  the  effect 
on  the  pressure  gauge.  Add  mercury  to  the  gauge  till 
the  mercury  in  the  short  arm  stands  again  at  the  mark, 
i.e.,  till  the  volume  occupied  by  the  two  gases  within  the 
flask  is  the  same  as  that  previously  occupied  by  the  air 
alone.  Next  introduce  two  or  three  drops  of  alcohol  or 
of  ether  [or  both,  one  after  the  other],  and  note  how 
several  gases  may  occupy  the  same  vessel  at  the  same  time. 
Caution !  In  working  with  alcohol  and  ether  take  great 
pains  to  avoid  fire,  as  both  are  readily  inflammable. 

Let  us  now  consider  our  suppositions  in  regard  to  the 
manner  in  which  a  cubic  inch  of  water,  after  passing 
into  the  condition  of  steam,  occupies  a  cubic  foot  of 
space.  By  experiment  we  have  just  found  that  when 
a  vessel  is  full  of  one  gas,  another,  and  still  another, 
can  be  added.  Hence  it  cannot  be  that  the  whole 
space  is  occupied  by  the  steam,  or  by  any  other  gas. 
It  is  true  that  it  may  be  thought  that  the  whole  mass 
of  the  steam  may  form  an  elastic  body,  and  that,  when 


184  THE   MODERN   PERIOD. 

another  gas  is  added,  this  elastic  body  of  steam  con- 
tracts, and  the  other  gas,  another  elastic  body,  occupies 
half  the  space.  But  if  any  given  portion  of  the  con- 
tents of  the  flask  be  drawn  off  and  examined,  it  will 
be  found  that  this  portion  contains  not  one  gas  alone 
but  some  of  all  that  have  been  added  to  the  flask.  In 
order  to  see  that  gases  mingle  and  do  not  push  one 
another  aside,  proceed  as  follows :  Take  a  Kjeldahl 
flask.  Heat  its  bulb  well  over  a  free  Bunsen  flame. 
Remove  the  flask  from  the  flame.  Drop  in  a  few 
small  crystals  of  iodine.  Cork  tightly.  Hold  the 
flask  to  the  light.  Shake,  and  note  that  the  colored 
iodine  vapor  mingles  with  the  air. 

We  have,  therefore,  proved  that  our  first  supposition, 
namely,  that  the  cubic  inch  of  water  simply  swells  out 
and  occupies  completely  the  whole  of  the  cubic  foot, 
cannot  be  an  expression  of  the  truth.  We  are  then 
forced  to  the  conclusion  that  the  water  is  made  up  of 
particles  —  the  molecules  of  Avogadro. 

Let  us  try  two  other  experiments  that  will  help  us 
in  deciding  whether  the  particles  are  large,  elastic,  and 
side  by  side  in  the  gaseous  condition  or  are  some  dis- 
tance apart,  i.e.,  whether  the  particles  themselves  swell 
up  or  keep  their  original  size  even  when  in  the  state  of 
steam. 

Experiment  24. 
Irregular  Expansion  of  Liquids.1 

Have  ready  three  small  [2  oz.  is  a  good  size]  bottles, 
all  of  the  same  size,  and  each  fitted  with  a  good  one- 
1  See  foot-note,  page  xxvii  of  the  Introduction. 


IRKEGTJLAR   EXPANSION   OF   LIQUIDS.  185 

hole  cork,  or,  better,  a  one-hole  rubber  stopper.  Fit  to 
each  stopper  a  piece  of  glass  tube  about  50cm  long  with 
its  lower  end  flush  with  the  under  side  of  the  stopper. 
Fill  the  first  bottle  with  water,  the  second  with  alcohol, 
and  the  third  with  ether. 

Caution !  Keep  all  fire  away  from  ether  and  from 
alcohol. 

Fill  each  bottle  to  the  brim,  and  insert  its  stopper, 
cautiously,  in  such  a  way  that  the  liquid  may  be  driven 
part  way  up  the  glass  tube,  and  that  no  air  may  be  left 
in  the  bottle.  Have  at  hand  a  vessel  of  water  large 
enough  to  hold  all  three  bottles  at  the  same  time,  and 
so  placed  that  it  may  be  heated,  forming  a  water-bath. 
Set  the  three  bottles  with  their  contents  side  by  side  in 
the  water-bath.  Make  a  mark  on  each  stem,  at  the 
point  where  the  liquid  stands.  Heat  the  water-bath, 
and  note  the  expansion  of  the  three  liquids.  Note  that 
the  ether  expands  by  far  the  most  rapidly.  When  the 
ether  shows  signs  of  boiling  remove  it  from  the  bath, 
and  set  it  away,  safe  from  fire.  Note  that  the  alcohol 
expands  the  next  in  amount.  When  the  alcohol  shows 
signs  of  boiling,  remove  it,  and  stop  heating  the  bath. 
Record  the  results. 


Experiment  25. 
Regular  Expansion  of  Gases.1 

Caution!     In  order  to  insure  success  in  this  experi- 
ment it  is  necessary  to  have  the  gases  experimented  on 
perfectly  dry,  to  have  all  joints  carefully  greased  and 
1  See  foot-note,  page  xxvii  of  the  Introduction. 


186  THE   MODERN   PERIOD. 

tight,  to  have  the  ice-bath  thoroughly  cooled  to  0°  C., 
and  to  make  sure  that  each  determination  is  carried 
on  with  the  apparatus  in  precisely  the  same  position ; 
that  each  time  the  delivery  tube  dips  the  same  distance 
under  the  water  in  the  pneumatic  trough ;  that  the  level 
of  the  water  in  the  measuring  cylinder  is,  each  time, 
kept  the  same  distance  above  the  water  in  the  trough 
at  the  time  the  volume  of  the  displaced  gas  is  read; 
and,  in  short,  that  all  conditions  are  the  same  for  each 
gas  tried. 

Have  ready  a  2  oz.  bottle  fitted  with  a  two-hole  rubber 
stopper.  Through  one  hole  of  the  stopper  pass  a  piece 
of  glass  tube  which  shall  reach  nearly  to  the  bottom  of  the 
bottle,  and  project  above  the  stopper  a  cm  or  two  when 
the  stopper  is  inserted  in  the  bottle.  Fit  to  the  upper 
end  of  this  tube  a  bit  of  rubber  tube  carrying  a  pinch- 
cock.  Through  the  second  hole  insert  the  end  of  a 
delivery  tube  arranged  so  that  when  the  bottle  is  placed 
in  the  water-bath  the  delivery  tube  will  reach  to  the 
pneumatic  trough.  Make  sure  that  the  bottle  is  per- 
fectly dry.  Carefully  grease  all  rubbers  to  make  all 
joints  air-tight.  Have  ready,  in  the  water-bath,  a 
mixture  of  crushed  ice  and  water,  or  snow  and  water 
[but  no  salt].  Use  much  ice,  as  a  pasty  mass  is  best. 
This  mixture  gives  a  uniform  temperature.  What  tem- 
perature? Insert  the  stopper  with  its  fittings,  open 
the  pinch-cock,  and  set  the  bottle  in  the  bath.  Make 
sure  that  the  bath  wholly  covers  the  bottle  and  reaches 
the  stopper.  Fill  the  bottle  with  dry  air  in  the  same 
way  that  you  filled  the  flask  in  Ex.  23.  When  dry  air 
has  passed  in  for  five  minutes,  close  the  pinch-cock, 


KEGULAR  EXPANSION  OF  GASES.       187 

and  disconnect  the  catch-bottle.  Make  sure  that  the 
bottle  is  still  well  surrounded  with  a  pasty  mass  of  ice 
and  water.  Open  the  pinch-cock  [for  a  moment  only] 
to  relieve  any  undue  pressure.  Place  your  graduate, 
inverted  and  full  of  water,  over  the  end  of  the  delivery 
tube  in  the  pneumatic  trough.  Heat  the  water-bath 
till  the  water  boils.  If  the  blast-lamp  flame  is  used 
the  water  will  boil  in  a  few  minutes.  Catch,  in  the 
graduate,  the  air  driven  out  by  the  expansion  of  the 
contents  of  the  bottle  while  the  temperature  rises  from 
the  freezing  point  to  the  boiling.  Note  the  number 
of  cc  caught. 

Again  make  an  iced  water-bath.  Now  pass  dry 
hydrogen  down  into  the  bottle  till  the  gas  which 
bubbles  up  from  the  pneumatic  trough  will,  when 
caught  in  a  tt,  burn  well.  Proceed  exactly  as  before, 
and  note  the  amount  of  hydrogen  driven  over  by  the 
expansion.  How  does  the  expansion  of  hydrogen 
compare  with  that  of  air? 

Again  make  an  iced  water-bath,  and  try  the  expan- 
sion of  an  equal  volume  of  illuminating  gas.  Take 
the  gas  from  the  gas  tap  at  your  desk.  Dry  the  gas 
by  passing  it  through  sulphuric  acid. 

Finally,  what  do  you  say  in  regard  to  the  expansion 
of  gases  ? 

Had  the  vapors  of  water,  of  alcohol,  and  of  ether 
been  tried  for  the  same  number  of  degrees  [100]  of 
temperature,  the  result  would  have  been  the  same, 
but,  of  course,  the  initial  temperature  must  have  been 
higher,  e.g.,  100°  instead  of  0°,  and  the  vapors  could 
not  be  caught  above  water.  Why  not?  Nor  could 


188  THE   MODERN   PERIOD. 

the  dioxide  of  carbon  be  tested  in  this  way,  for  it  is 
enough  soluble  in  water  to  prevent  an  accurate  deter- 
mination, if  measured  above  water. 

Let  us  consider  the  meaning  of  the  results  of  Exs.  24 
and  25.  We  find  that  every  substance  in  the  liquid 
form  has  its  own  special  rate  of  expansion.  But  if 
the  temperature  is  so  high  that  the  liquids  have  been 
changed  to  gases,  the  expansion  of  the  substances  in 
the  gaseous  state  is  for  each  about  the  same.  Now  it 
must  be  the  effect  of  the  particles  acting  each  on  the 
other  that  causes  the  different  rates  of  expansion  for 
liquids,  but,  if  we  assume  that  these  same  particles, 
without  change  of  size,  are  driven  so  far  apart,  in 
the  conversion  of  the  liquids  into  gases,  that  they 
have  little  or  no  effect  upon  each  other,  it  seems  natural 
that  heat  should  have  the  same  effect  on  one  gas 
that  it  does  on  another,  i.e.,  that  all  gases  should 
have  the  same  rate  of  expansion,  particularly,  if  we 
assume,  with  Avogadro,  that  there  are,  in  equal  vol- 
umes, equal  numbers  of  the  particles.  From  a  con- 
sideration of  these  facts  and  many  others,  physicists 
have  come  to  the  conclusion  that  matter  is  made  up 
of  minute  particles,  —  that,  in  the  state  of  gas,  these 
particles  are  not  closely  packed,  but,  in  fact,  that  the 
spaces  between  them  are  very  large  in  comparison 
with  the  size  of  the  particles  themselves ;  that,  in  the 
liquid  state,  the  particles  are  near  together,  and  influ- 
ence one  another  ;  and  that,  in  the  solid  state,  the 
particles  are  still  nearer  together,  and  cannot  move 
from  their  relative  positions. 

It  is,  moreover,  believed  that  all  molecules  are  in 


SIZE   OF   THE   MOLECULES.  189 

constant  motion,  —  that,  in  the  case  of  gases,  they  are 
moving  about  among  themselves,  with  great  velocity; 
that,  in  the  case  of  liquids,  the  motion  is  much  more 
restricted;  and  that,  in  the  case  of  solids,  the  motion 
is  one  of  vibration  or  of  rotation,  and  not  a  changing 
of  place. 

There  seems  no  hope  that  the  best  of  microscopes 
will  ever  be  able  to  show  the  molecules.  The  phy- 
sicists estimate  that  the  diameters  of  the  molecules 
of  some  substances,  —  as  alum  and  albumen,  —  that 
have  remarkably  large  molecules,  range  from  the  one 
10,776,000th  of  an  inch  to  the  one  5,000,000th  of 
an  inch.  But  "the  best  microscopes  made  to-day 
will  enable  one  to  see  as  barely  visible  a  point  the 
one  hundred-thousandth  of  an  inch,  so  that  such  a 
microscope  would  need  to  be  as  much  more  powerful 
than  it  now  is  as  one  hundred  thousand  is  contained 
in  five  millions,  that  is,  fifty  times,  in  order  to  see 
the  albumen  molecule,  and  for  the  alum  molecule  as 
many  times  as  one  hundred  thousand  is  contained  in 
ten  million  seven  hundred  thousand,  that  is,  one 
hundred  and  seven  times.  Now,  one  who  is  familiar 
with  the  microscope  would  probably  admit  that  one 
might  be  made  through  improved  methods  of  making 
and  working  glass  hereafter  to  be  discovered,  two 
or  three,  or  even  ten  times  better  than  the  best  we 
have  now ;  but  the  idea  of  one  being  made  fifty  or  a 
hundred  times  more  powerful  than  we  have  to-day, 
I  do  not  think  would  be  allowed  to  have  any  degree 
of  probability.  The  powers  of  the  microscope  have  not 
been  doubled  within  the  last  fifty  years,  and  I  suppose 


190  THE   MODERN   PERIOD. 

more  time  and  ingenuity  have  been  given  to  the  problem 
of  improving  it  than  will  ever  be  given  to  it  in  the 
same  interval  again."  l 

To  give  some  idea  of  the  actual  size  of  the  molecules 
of  water,  it  may  be  added  that  it  has  been  estimated 
that  if  a  drop  of  water  should  be  magnified  to  the  size 
of  the  earth,  the  molecules  would  appear  not  larger 
than  cricket-balls,  and  not  smaller  than  small  lead  shot. 

The  great  molecular  theory,  which  has  sprung  from 
the  hypothesis  made  by  Avogadro,  serves  to  explain 
phenomena,  and  by  its  application  undiscovered  facts 
have  been  predicted  and  verified  time  and  again.  Still 
we  must  remember  that  it  is  only  a  theory,  that  we 
never  have  seen  the  molecules,  and,  after  all,  there 
may  not  be  such  things  as  molecules,  but  this  theory 
is  based  on  facts  of  a  very  substantial  nature,  and 
we  cannot  help  thinking  that  in  it  lie  the  elements, 
at  least,  of  some  absolute  truth.  We  must,  however, 
in  all  our  work,  bear  in  mind  the  distinction  there  is, 
and  always  must  be,  between  facts  and  the  hypotheses 
and  theories  that  are  put  forth  to  explain  the  facts. 
"When,  however,"  to  quote  from  Professor  Cooke,2 
44  we  come  to  study  the  history  of  science,  the  dis- 
tinction between  fact  and  theory  obtrudes  itself  at 
once  upon  our  attention.  We  see  that,  while  the 
prominent  facts  of  science  have  remained  the  same,  its 
history  has  been  marked  by  very  frequent  revolutions 
in  its  theories  or  systems.  The  courses  of  the  planets 

1  A.  E.  Dolbear.     "  Matter,  Ether  and  Motion." 

2  "The  New  Chemistry."     Let  every  student  who  wishes  to  know 
more  about  the  molecular  theory  get  this  book,  and  study  the  first 
chapters. 


PACT   AND   THEORY.  191 

have  not  changed  since  they  were  watched  by  the 
Chaldean  astronomers,  three  thousand  years  ago ;  but 
how  differently  have  their  motions  been  explained  — 
first  by  Hipparchus  and  Ptolemy,  then  by  Copernicus 
and  Kepler,  and  lastly  by  Newton  and  Laplace !  — 
and,  however  great  our  faith  in  the  law  of  universal 
gravitation,  it  is  difficult  to  believe  that  even  this 
grand  generalization  is  the  final  result  of  astronomical 
science. 

"Let  me  not,  however,  be  understood  to  imply  a 
belief  that  man  cannot  attain  to  any  absolute  scientific 
truth ;  for  I  believe  that  he  can,  and  I  feel  that  every 
great  generalization  brings  him  a  step  nearer  to  the 
promised  goal.  Moreover,  I  sympathize  with  that 
beautiful  idea  of  Oersted,  which  he  expressed  in  the 
now  familiar  phrase,  'The  laws  of  Nature  are  the 
thoughts  of  God'  .  .  .  Through  the  great  revolu- 
tions which  have  taken  place  in  the  forms  of  thought, 
the  elements  of  truth  in  the  successive  systems  have 
been  preserved,  while  the  error  has  been  constantly 
eliminated  ;  and  so,  as  I  believe,  it  always  will  be, 
until  the  last  generalization  of  all  brings  us  into  the 
presence  of  that  law  which  is  indeed  the  thought  of 
God." 

For  Review.  —  §§  7,  8,  and  9.  Show  how  Dalton's 
atomic  hypothesis  explained  two  of  the  fundamental 
laws  of  chemistry.  What  is  meant  by  the  term  mole- 
cule? How  does  a  molecule  usually  differ  from  an 
atom?  Do  simple  substances  have  molecules?  Give 
some  of  Dalton's  symbols,  and  tell  what  he  wished 


192  THE  MODERN    PERIOD. 

each  to  represent.  State  why  Dalton's  value  for  the 
relative  weight  of  the  oxygen  atom  may  have  been 
far  from  correct.  Describe,  briefly,  the  work  of  Gay- 
Lussac,  which  led  to  the  discovery  of  a  fourth  great  law 
of  chemistry.  State  the  law  of  definite  proportions 
by  volume.  Who  was  Avogadro  ?  When  did  he  make 
his  famous  suggestion?  Who,  soon  after,  made  the 
same  suggestion  ?  What  was  this  famous  suggestion  ? 
What  three  suppositions  can  be  made  in  regard  to  the 
change  of  volume  that  takes  place  when  a  cubic  inch  of 
water  passes  into  steam?  Show  why  two  of  these 
suppositions  cannot  be  expressions  of  the  truth.  Give 
reasons  for  thinking  that  the  third  supposition  is  an 
expression  of  the  truth.  What  is  believed  in  regard  to 
the  movements  of  the  molecules  ?  What  is  believed 
in  regard  to  the  actual  sizes  of  the  molecules  ? 


§  10.     DETERMINING  ATOMIC  WEIGHTS. 

The  law  of  Gay-Lussac,  together  with  the  hy- 
pothesis of  Avogadro,  proved  of  great  assistance  in 
seeking  to  establish  the  true  weights  of  atoms  and  of 
molecules.  For  instance,  we  can  now  prove  that  the 
molecule  of  hydrogen  gas  contains  two  atoms  of  hydro- 
gen. If  one  volume  of  hydrogen  gas  is  mixed  with  one 
volume  of  chlorine  gas  and  exploded,  it  is  found  that 
the  resulting  hydrochloric  acid  gas  occupies  just  as 
much  space  as  the  two  factors  before  the  explosion, 
i.e.,  one  volume  of  hydrogen  plus  one  volume  of  chlo- 


TRUE   ATOMIC   WEIGHTS.  193 

rine  gives  two  volumes   of   hydrochloric  acid.      This 
may  be  represented  thus  : 


hydro- 
chloric acid 
gas 


hydro- 
chloric acid 


Let  us  assume  that  our  unit  volume  here  contained 
just  1,000000  molecules.  Then,  by  the  hypothesis  of 
Avogadro,  if  there  are  1,000000  molecules  in  the  one 
volume  of  hydrogen,  there  must  be  1,000000  mole- 
cules of  chlorine  in  the  one  volume  of  chlorine,  and 
2,000000  molecules  of  hydrochloric  acid  in  the  result- 
ing two  volumes  of  hydrochloric  acid  gas.  Analysis 
shows  that  every  molecule  of  hydrochloric  acid  con- 
tains both  hydrogen  and  chlorine,  therefore,  in  the 
2,000000  molecules  of  hydrochloric  acid  there  must 
be  at  least  2,000000  atoms  of  hydrogen,  but  these 
2,000000  atoms  of  hydrogen  came  from  only  1,000000 
molecules  of  hydrogen  gas,  hence  we  are  forced  to 
believe  that  every  molecule  of  hydrogen  has  two  atoms 
of  hydrogen  in  it. 

If,  then,  a  single  atom  of  hydrogen  weighs  one  micro- 
crith,  and  we  have  proved  that  there  are  at  least  two 
atoms  of  hydrogen  in  the  molecule  of  hydrogen  gas, 
the  molecular  weight,  i.e.,  the  weight  of  a  molecule 
of  hydrogen,  must  be  at  least  two  microcriths.  As 
no  proof  has  ever  been  presented  to  show  that  there 
are  more  than  two  atoms  in  the  molecule  of  hydrogen, 
the  accepted  molecular  weight  of  hydrogen  is  two 
microcriths. 

Experiment  shows,  moreover,  that  two  volumes  of 
hydrogen  and  one  volume  of  oxygen  join  and  form 


194 


THE   MODERN    PERIOD. 


two    volumes   of    steam.      This    may   be   represented 
thus  : 


hydrogen 

hydrogen 

steam 

steam 

Let  us  assume,  as  before,  that  each  single  volume  con- 
tains 1,000000  molecules.  Then,  as  the  three  volumes 
are  condensed  to  two  volumes,  the  3,000000  molecules 
must,  by  the  hypothesis  of  Avogadro,  be  condensed  to 
2,000000  molecules.  Analysis  shows  that  each  mole- 
cule of  steam  has  in  it  at  least  one  atom  of  oxygen.  As 
there  are  2,000000  of  the  steam  molecules,  there  must 
be  2,000000  oxygen  atoms.  These  2,000000  oxygen 
atoms  came  from  1,000000  oxygen  molecules.  Hence 
each  molecule  of  oxygen  must  have  at  least  two  atoms 
of  oxygen.  Finally,  as  there  were  2,000000  molecules 
of  hydrogen  used,  and  each  molecule,  as  proved,  on  page 
193,  had  two  atoms  of  hydrogen,  4,000000  atoms  of 
hydrogen  must  have  gone  into  the  2,000000  molecules 
of  steam.  Hence  each  molecule  of  steam  must  have  two 
atoms  of  hydrogen.  And  as  there  is  at  least  one  oxygen 
atom  in  each  molecule  of  steam,  we  conclude  that  the 
eomposition  of  water  [steam]  is  two  atoms  of  hydrogen 
and  one  atom  of  oxygen.  If,  then,  the  oxygen  out- 
weighs the  hydrogen  8:1,  the  single  atom  of  oxygen, 
being  eight  times  as  heavy  as  two  atoms  of  hydrogen, 
must  be  sixteen  times  as  heavy  as  one  atom  of  hydro- 
gen. And  sixteen  is  the  atomic  weight  we  assign  to 
oxygen.  If  it  is  true  that  there  are  two  and  only  two 
atoms  of  oxygen  in  the  molecule  of  oxygen  gas,  what 
is  the  molecular  weight  of  oxygen?  What  is  the 
molecular  weight  of  water? 


MOLECULAR    WEIGHT    DETERMINATIONS.          195 


§  11.     DETERMINING  MOLECULAR  WEIGHTS. 

If  we  accept  the  hypothesis  of  Avogadro  as  an 
expression  of  the  truth,  we  can  calculate  the  molecular 
weights  of  all  substances  which  are  naturally  in  the  gas- 
eous state  or  can  be  converted  into  this  state,  e.g.,  water 
can  have  its  molecular  weight  taken  when  it  is  in  the 
form  of  steam,  and  some  solid  substances,  as  paraffines, 
can  be  heated  till  vaporized  in  order  to  have  their  molec- 
ular weights  taken.  The  determination  of  molecular 
weights  by  means  of  Avogadro's  hypothesis  is  called 
the  Physical  Method  for  Molecular  Weight  Deter- 
minations. It  is  a  very  simple  method. 

If  equal  volumes  of  all  aeriform  substances  contain 
the  same  number  of  molecules,  the  weight  of  any  one 
molecule  must  bear  the  same  ratio  to  that  of  any  other 
molecule  that  the  weight  of  a  given  volume  of  the  first 
gas  bears  to  the  weight  of  the  same  volume  of  the 
second  gas.  Having  proved  that  a  molecule  of  hydro- 
gen weighs  2mc  [two  microcriths],  if  we  get  the  weight 
in  grams  of  a  given  volume  of  hydrogen  gas  and  the 
weight  in  grams  of  the  same  volume  of  some  other  gas, 
and  reckon  how  many  times  heavier  the  given  volume 
of  the  latter  is  than  the  same  volume  of  hydrogen,  or, 
in  other  words,  if  we  determine  the  specific  gravity  of 
the  second  gas  in  reference  to  hydrogen  [instead  of  to 
air  or  to  water]  as  a  standard,  and  multiply  by  2,  we 
shall  have  the  molecular  weight  of  the  second  gas. 
The  reason  it  is  necessary  to  multiply  by  2  is  because, 
although  each  molecule  of  the  second  gas  is  just  as 
many  times  as  heavy  as  a  molecule  of  hydrogen,  as  is 


196  THE   MODEEN   PERIOD. 

the  whole  volume  of  the  second  gas  than  an  equal  vol- 
ume of  hydrogen  gas,  yet  the  molecule  of  hydrogen 
itself  weighs  2mc,  being  composed  of  two  atoms,  each  of 
which  contains  unit  quantity,  that  is  lmc,  of  hydrogen. 

Let  us  determine  some  molecular  weights  by  the 
physical  method. 

Experiment  26. 

Determination  of  Molecular  Weights  by  the  Physical 
Method. 

A.     Molecular  Weight  of  Carbonic  Dioxide. 

We  have  already  got  the  sp.  gv.  of  carbonic  dioxide 
referred  to  air  and  to  hydrogen.  See  Ex.  14,  page  145, 
and  Ex.  15,  page  148.  Now  get  the  molecular  weight 
of  .carbonic  dioxide. 

As  coal  gas  and  air,  two  other  substances  whose  sp. 
gv.  we  have  determined,  are  mixtures  and  not  chemical 
compounds,  they  have  no  such  things  as  molecular 
weights,  for  they  contain  molecules  of  different  sub- 
stances. 

B.     Molecular  Weight  of  Oxygen  Gas. 

Determine  the  sp.  gv.  of  oxygen  gas  by  the  method 
of  Ex.  14,  page  145.  From  this  result  get  the  molec- 
ular weight  of  oxygen  gas. 

Although  the  physical  method  for  determining  mo- 
lecular weights  is  a  very  simple  and  useful  one,  it  is 
limited  in  its  application  to  substances  which  are  gases 
or  can  be  converted  into  vapors.  The  molecular  weights 


MOLECULAR   WEIGHT   DETERMINATIONS.         197 

of  other  substances  are  determined  by  what  is  called  the 
chemical  method.  In  using  the  chemical  method  it  is 
always  necessary  to  get  a  start  by  the  physical  method, 
i.e.,  the  determination  of  the  molecular  weight  of  some 
gas  is  first  made  from  its  sp.  gv.  referred  to  hydrogen. 
Then  a  chemical  change  is  brought  about,  in  which 
both  the  substance  whose  molecular  weight  it  is  desired 
to  find  and  the  gas  whose  molecular  weight  is  known 
are  involved. 

If  one  molecule  of  the  substance  whose  molecular 
weight  is  known  always  produced  one  molecule  of  the 
substance  whose  molecular  weight  is  required,  or  vice 
versa,  the  "application  of  the  chemical  method  would  be 
extremely  simple,  for  the  gram  weight  of  the  first 
would  be  to  the  gram  weight  of  the  second  as  is  the 
molecular  weight  of  the  first  to  the  molecular  weight 
of  the  second.  But  as  one  molecule  of  the  known 
often  furnishes  either  more  than  enough  atoms  to  form 
just  one  molecule  of  the  unknown  or  less  than  enough 
[and  vice  versa]  the  application  is  difficult  and  usually 
requires  a  study  of  many  chemical  changes  into  which 
the  unknown  enters  before  the  number  of  atoms  in  the 
molecule  and  the  correct  molecular  weight  can  be  fixed. 


Experiment  27. 

Determination  of  Molecular  Weights  by  the  Chem- 
ical Method. 

We  have  already  determined,  by  the  physical  method, 
the  molecular  weight  of  oxygen.     Let  us  assume  that 


198  THE   MODERN   PEEIOD. 

we  have  found  this  weight  to  be  32mc.  Now  if  we 
bring  about  some  chemical  change  in  which  oxygen  is 
involved,  we  can  get  the  molecular  weight  of  some 
other  substances. 

A.     Molecular  "Weight  of  Chlorate  of  Potassium. 

If  your  chlorate  of  potassium  is  not  known  to  be 
pure,  dissolve  10-20  g.  of  it  in  hot  water  and  recrystal- 
lize.  Powder  the  crystals  and  dry  at  a  temperature 
between  100°  and  200°  C. 

In  a  weighed  porcelain  crucible  put  about  two  grams 
of  pure  dry  chlorate  of  potassium.  Get  the  exact  weight 
of  the  chlorate.  Put  the  cover  on  the  crucible.  This 
cover  should  be  weighed  also,  that  its  weight  may  be 
added  in  case  there  is  any  spattering.  Heat  the  chlo- 
rate, gently,  with  a  Bunsen  burner,  but  take  care  that 
the  contents  of  the  crucible  do  not  foam  up  and  pour  over 
the  sides.  After  the  chlorate  has  melted  continue  heat- 
ing till  the  mass  again  becomes  solid.  Then  apply  the 
blast-lamp,  gently,  till  the  mass  again  melts.  Just  as 
soon  as  the  second  melting  has  taken  place,  remove 
the  flame,  let  cool,  and  weigh.  Again  just  melt  the 
substance,  let  cool,  and  weigh.  Continue  till  the 
weight  is  constant.  Note  the  loss  in  weight  caused 
by  the  escape  of  the  oxygen. 

We  can  now  calculate  the  molecular  weight  of 
chlorate  of  potassium.  In  making  our  calculations, 
however,  we  meet  with  one  difficulty.  We  do  not 
know  how  many  atoms  of  oxygen  each  molecule  of 
chlorate  has  furnished  for  making  the  molecules  of  the 
oxygen  gas.  If  one  molecule  of  the  chlorate  has  lost 


MOLECULAR    WEIGHT    DETERMINATIONS.         199 

one  atom,  only,  of  oxygen,  the  ratio  of  the  weight  of 
the  chlorate  to  the  weight  of  the  oxygen  gas  gone  off 
is  x  :  half  32,  or  16,  because  we  have  proved  that  there 
are  two  atoms  of  oxygen  in  the  molecule  of  oxygen  gas, 
also  that  its  total  molecular  weight  is  32.  If  every 
molecule  of  the  chlorate  has  lost  two  atoms  of  oxygen, 
the  ratio  is  x  :  32,  because  the  two  atoms  of  oxygen  are 
just  enough  to  form  a  single  molecule  of  oxygen  gas. 
If,  however,  every  molecule  of  chlorate  has  lost  three 
atoms  of  oxygen,  the  ratio  is  x  :  one  and  a  half  times 
32,  or32  +  16  =  48.  A  study  of  the  chemical  changes 
into  which  chlorate  of  potassium  enters  shows  that  it 
has  three  atoms  of  oxygen,  and  all  are  given  up  in  this 
experiment.  Hence  in  making  our  calculations  we  must 
consider  that  one  molecule  of  the  chlorate  has  furnished 
enough  oxygen  to  form  a  molecule  and  a  half  of  oxygen 
gas.  Therefore  the  molecular  weight  of  one  molecule  and 
a  half  of  oxygen  [32  + 16  =  48]  is  to  the  molecular  weight 
of  one  molecule  of  the  chlorate  [#],  as  is  the  weight  in 
grams  of  the  oxygen  given  off,  to  the  weight  in  grams 
of  the  chlorate  taken.  Make  the  proper  proportion,  and 
get  the  molecular  weight  of  chlorate  of  potassium. 

B.   Molecular  "Weight  of  Chloride  of  Potassium. 

From  the  data  of  A  get  the  molecular  weight  for  the 
chloride  of  potassium  which  was  left  in  the  crucible 
after  heating. 

Note.  It  is  obvious  that  if  we  can  find  any  chemical 
changes  in  which  either  the  chlorate  of  potassium  or 
the  chloride  enters,  and  if  we  can  weigh  the  factors 


200  THE   MODERN   PERIOD. 

and  the  products,  we  can  make  proportions  and  calcu- 
late the  molecular  weights  for  the  other  substances 
involved  in  the  changes.  We  are,  of  course,  sometimes 
limited,  because  we  cannot  always  tell  just  how  many 
atoms  leave  one  molecule,  or  how  many  go  to  some 
other.  But  it  is  seldom  that  we  are  left  with  nothing  to 
help  us  in  our  choice  between  several  multiples. 

C.  Molecular  Weight  of  Sulphate  of  Potassium. 

In  getting  the  molecular  weight  of  sulphate  of 
potassium  we  shall  take  advantage  of  the  fact  that  we 
have  just  determined  the  molecular  weight  of  chloride 
of  potassium,  and  of  the  fact  that  the  sulphate  can  be 
made  from  the  chloride  by  the  action  of  sulphuric  acid. 

Put  in  a  weighed  porcelain  crucible  a  small  amount 
[from  lg  to  1.5g]  of  finely  powdered,  dry,  c. p.  chloride  of 
potassium.  Get  the  exact  weight  of  the  chloride  used. 
Add  a  little  sulphuric  acid  [c.p.  is  best],  drop  by  drop, 
while  you  pass  the  Bunsen  burner  flame,  now  and  then, 
below  the  crucible.  Heat,  gently  at  first,  with  the 
Bunsen  burner  as  long  as  fumes  come  readily,  but  avoid 
all  spattering  out.  Finally,  apply  the  blast-lamp  flame 
till  the  molten  mass  becomes  a  spongy  solid.  Cool  and 
weigh.  Heat  to  constant  weight.  As  it  takes  two 
molecules  of  the  chloride  to  make  one  of  the  sulphate, 
it  is  necessary,  in  making  our  proportion  in  this  case, 
to  take  double  the  molecular  weight  of  the  chloride  to 
compare  with  the  molecular  weight  of  the  resulting 
sulphate. 

Find,  also,  the  molecular  weight  of  sulphuric  acid, 
assuming  that  it  takes  one  molecule  of  the  acid  to 


MOLECULAR   WEIGHT  DETERMINATIONS.         201 

produce  one  molecule  of  the  sulphate  from  the  two 
molecules  of  the  chloride,  and  that  the  amount  of  the 
sulphuric  acid  needed  to  act  on  lg  of  chloride  was  0.65g. 
Finally,  get  the  molecular  weight  of  hydrochloric  acid, 
assuming  that  during  the  change  of  the  chloride  into 
the  sulphate  there  escaped  two  molecules  of  hydro- 
chloric acid  gas,  and  that  the  weight  of  this  gas  pro- 
duced by  lg  of  the  chloride  was  0.49g. 

Knowing  the  molecular  weights  of  sulphuric  and 
hydrochloric  acids,  we  could,  in  a  similar  manner,  get 
molecular  weights  for  substances  with  which  these 
acids  react. 

Neither  the  physical  nor  the  chemical  method  for 
determining  molecular  weights  can  be  applied  univer- 
sally. The  physical  method  is  confined  to  substances 
which  are  naturally  gases,  or  can  be  converted  into 
vapors  at  a  comparatively  low  temperature ;  while  the 
chemical  is  limited,  inasmuch  as  a  start  has  to  be  made 
from  some  determination  obtained  by  the  physical. 

For  Review.  —  §§  10  and  11.  Prove  [using  the  law 
of  Gay-Lussac  and  the  hypothesis  of  Avogadro]  that 
the  molecule  of  hydrogen  gas  contains  two  atoms  of 
hydrogen;  that  a  molecule  of  water  [steam]  has  two 
atoms  of  hydrogen;  that  the  weight  of  an  atom  of 
oxygen  is  16  microcriths.  What  is  a  microcrith? 
What  is  a  crith  ?  What  is  the  weight  [in  microcriths] 
of  a  molecule  of  hydrogen  ?  Of  a  molecule  of  oxygen  ? 
Of  a  molecule  of  water?  Define  the  physical  method 
for  determining  molecular  weights.  Describe  an  experi- 
ment that  illustrates  this  method.  Define  the  chemical 


202  THE  MODERN   PERIOD. 

method  for  determining  molecular  weights.  Describe 

an  experiment  that  illustrates  this  method.  In  what 

respect   is    the    physical    method    limited?  In    what 
respect  is  the  chemical  method  limited  ? 


§  12.     SPECIFIC  HEAT. 

Another  aid  in  determining  which  multiple  of  the 
combining  number  should  be  taken  for  the  atomic 
weight,  was  found  in  the  relation  discovered  to  exist 
between  the  specific  heats  of  elementary  substances  and 
their  atomic  weights. 

In  the  year  1819  this  discovery  was  announced  by 
two  French  chemists,  Dulong  and  Petit. 

The  specific  heat  of  any  substance  may  be  defined  as 
the  amount  of  heat  required  to  raise  the  temperature  of 
one  gram  of  that  substance  one  degree,  compared  with 
the  amount  of  heat  required  to  raise  the  temperature  of 
the  same  amount  [one  gram]  of  a  standard  substance 
[water]  the  same  distance  [one  degree]. 

Be  sure  you  see  clearly  the  distinction  between 
temperature  and  heat  itself.  The  temperature  of  a 
body  is  simply  its  state  in  respect  to  heat  or  cold. 
What  the  heat  itself  is  we  do  not  know.  The  most 
reasonable  explanation  of  heat  is  that  it  is  motion  of 
some  kind.  If,  for  instance,  a  piece  of  iron,  as  a  nail, 
is  pounded  vigorously  with  a  hammer,  it  soon  becomes 
too  hot  to  be  held. 


HEAT.  203 

Experiment  28. 
Transference  of  Motion. 

Take  a  nail,  and  having  placed  it  on  some  hard  sub- 
stance that  will  not  be  harmed,  pound  it  vigorously 
with  a  hammer  till  it  becomes  too  hot  to  be  held. 

It  is  believed  that  at  the  moment  the  motion  of  the 
hammer  is  arrested,  the  particles  of  the  iron  receive  a 
kind  of  motion,1  which  is  manifested,  as  we  say,  by  an 
increase  of  temperature.  It  is  not  thought  that  the 
particles  of  a  solid  move  around  among  one  another,  but 
that  the  motion  is  a  vibratory  or  a  rotary  one  ;  the 
greater  the  vibration  or  the  rotation,  the  greater  the 
heat.  The  particles  of  gases,  however,  are  supposed  to 
change  places  very  rapidly. 

It  might  be  thought  that  the  amount  of  motion,  i.e., 
the  amount  of  heat,  imparted  to  a  gram  of  one  sub- 
stance in  order  to  raise  its  temperature  one  degree, 
would,  if  imparted  to  a  gram  of  any  other  substance, 
cause  a  rise  of  just  the  same  extent,  but  experiment 
shows  that  this  is  not  so.  When  exposed  to  the  same 
source  of  heat,  some  substances  reach  a  given  tempera- 
ture quicker  than  others.  Of  all  substances,  water  is 
the  slowest  to  reach  the  given  temperature;  e.g.,  the 
amount  of  heat  that  will  raise  a  given  number  of  grams 
of  water  from  0°  C.  to  10°  C.  would  raise  the  same 
amount  of  iron  from  0°  C.  to  88°  C.;  the  same  amount 
of  mercury  to  300°  C.;  the  same  amount  of  silver  to 
175°  C.;  and  so  on. 

1  It  is  supposed  that,  even  before  struck  with  the  hammer,  the  parti- 
cles had  a  considerable  amount  of  this  same  kind  of  motion. 


204  THE  MODERN   PERIOD. 

The  amount  of  heat  that  is  required  to  raise  one 
gram  of  water  one  degree  is  called  a  calorie,1  and  is  the 
unit  taken  for  determinations  of  quantities  of  heat,  just 
as  the  degree  is  the  unit  taken  for  temperatures.  The 
specific  heat  of  a  substance  may  also  "be  defined  as  the 
number  of  calories  required  to  raise  a  given  weight  of 
the  substance  a  given  number  of  degrees  compared  with 
the  number  of  calories  required  to  raise  the  same  weight 
of  water  the  same  number  of  degrees.  If  the  weight 
selected  is  a  gram  for  both  the  water  and  the  other 
substance,  and  the  distance  the  temperature  is  to  be 
raised  is  one  Centigrade  degree,  then  the  number  ex- 
pressing the  specific  heat  of  the  other  substance  is 
always  a  fraction,  and  less  than  1 ;  for  it  takes  but  one 
unit  of  heat  to  raise  one  gram  of  water  1°  C.,  and  it 
takes  less  heat  for  a  gram  of  every  other  substance. 

Let  us  determine  the  specific  heats  of  a  few  sub- 
stances. 

First,  prepare  a  calorimeter,  i.e.,  a  piece  of  appara- 
tus for  measuring  heat  quantities.  Take  a  beaker  that 
holds  about  200CC,  and  a  second  beaker  somewhat 
larger.  The  second  beaker  should  be  of  such  a  size 
that  when  the  200CC  one  is  set  in  it  there  will  be  a 
space  of  l-2cm  between  the  walls.  Place  a  layer  of 
cotton-wool  on  the  bottom  of  the  larger  beaker ;  on 
this  cotton  set  the  smaller  beaker,  and  pack  loosely 
the  space  between  the  walls  with  cotton.  This  packing 
will  serve  to  prevent  a  considerable  loss  of  heat  in 
subsequent  work. 

1  This  small  amount  of  heat  is  sometimes  called  the  millicalorie,  in 
distinction  from  the  large  calorie  more  frequently  used,  which  is  the 
amount  of  heat  it  takes  to  raise  one  kilogram  of  water  one  degree. 


SPECIFIC    HEAT   OF   ZINC.  205 

Experiment  29. 
Specific  Heat  of  Zinc.1 

Have  ready  the  calorimeter  just  made,  a  thermome- 
ter, and  a  long,  wide  tt.2  Also  have  ready  some  water, 
boiling,  in  a  large  beaker,  iron  pot,  or  any  other  suit- 
able vessel.  Twist  around  the  neck  of  the  large  tt  a 
piece  of  wire  stiff  enough  to  serve  as  a  handle.  Pour 
exactly  100CC  of  cold  water3  into  the  inner  beaker  of 
the  calorimeter,  and  exactly  50g  of  zinc  [dust  or  fine 
granular]  into  the  large  tt.  Warm  the  thermometer 
somewhat  in  the  steam  of  the  boiling  water,  and  then 
take  the  temperature  of  the  boiling  water.  Cool  the 
thermometer  somewhat,  and  set  it  in  the  water  in  the 
calorimeter.  Heat  the  zinc  to  the  temperature  of  the 
boiling  water  by  plunging  the  large  tt  and  its  charge 
well  down  into  the  boiling  water,  and  keeping  them 
there  at  least  five  minutes.  Be  sure  the  water  con- 
tinues to  boil  well.  A  bit  of  cotton  should  be  stuffed 
in  the  mouth  of  the  tt  to  prevent  spray  going  in. 

With  the  thermometer  stir  the  water  in  the  calorim- 
eter, and  note  its  temperature  accurately  to  a  tenth  of 
a  degree.  Remove  the  thermometer  ;  also  the  plug  of 
cotton  from  the  mouth  of  the  tt.  Then  at  once  pour 
the  zinc  into  the  cool  water,  again  insert  the  thermom- 
eter, stir  as  long  as  the  temperature  continues  to  rise, 

1  See  foot-note,  page  xxvii  of  the  Introduction. 

2  This  tt  should  be  about  15cm  long,  and,  if  possible,  2cm  wide. 

3  When  ice   or  snow  or  even  very  cold  water  is  at  hand,  it  is 
well  to  cool  this  water  [before  measuring  out  the  100CC]  a  few  degrees 
below  the  temperature  of  the  laboratory.     Why  ? 


206  THE   MODERN    PERIOD. 

and  note  the  total  rise  of  the  temperature,  —  accurately 
to  a  tenth  of  a  degree. 

In  spite  of  the  cotton  packing  there  will  be  some  loss 
of  heat,  and  the  temperature  will  not  rise  quite  as  far 
as  it  should.  If  at  the  start  the  water  in  the  calorim- 
eter was  cooled  about  as  much  below  the  temperature 
of  the  room  as  it  is  heated  above  that  temperature  at 
the  end  of  the  experiment,  it  is  fair  to  suppose  that  the 
cold  water  at  the  start  gains,  abnormally,  about  as  much 
heat  as  the  warm  water  at  the  finish  loses,  and  that  the 
result  of  an  experiment  performed  in  this  way  is  more 
accurate  than  the  result  of  one  in  which  no  such  pre- 
caution is  taken.  Then,  too,  some  of  the  heat  from  the 
zinc  is  lost  in  heating  the  thermometer,  and  some  in 
heating  the  beaker  itself.  Owing  to  such  errors  as 
these,  the  result  of  this  experiment  will  not  compare 
very  well  with  results  obtained  where  the  utmost  pre- 
cautions are  taken,  and  allowance  is  ma'de  for  the  heat 
absorbed  by  thermometer  and  calorimeter.  However,  it 
is  easy,  with  this  apparatus,  to  get  results  near  enough 
to  the  truth  to  form  good  data  for  subsequent  work. 

Knowing  the  amount  of  water  that  was  heated,  and 
the  amount  of  zinc  that  gave  the  heat,  and  having  noted 
the  number  of  degrees  that  the  temperature  of  the 
water  rose,  and  the  number  that  the  temperature  of  the 
zinc  fell,  we  can  calculate  the  specific  heat  of  zinc. 
Bear  in  mind  that  a  calorie  is  the  amount  of  heat  it 
takes  to  raise  one  gram  of  water  one  degree,  and  state  : 

[1]  The  number  of  units  of  heat  that  the  whole  of 
the  water  gained. 


•.•»  ras 

TSlVBKSr 

SPECIFIC    HEATS.      xS 


[2]  The  number  of  units  of  heat  that  the  50g  of 
zinc  lost. 

[3]  The  number  of  units  of  heat  that  the  50g 
would  have  lost  if  they  had  fallen  only  one  degree  of 
temperature. 

[4]  The  number  of  units  of  heat  that  one  gram  of 
zinc  would  have  lost  in  falling  one  degree. 

As  it  would  take  just  as  much  heat  to  raise  one  gram 
of  zinc  one  degree  as  it  lost  in  falling  one  degree,  the 
number  obtained  for  [4]  must  represent  the  specific 
heat  of  zinc. 


Experiment  3O. 
Specific  Heat  of  Iron.1 

In  a  manner  similar  to  that  of  Experiment  29,  get 
the  specific  heat  of  iron.  Use  iron  in  the  form  of  filings 
or  small  nails. 


Experiment  31. 
Specific   Heat.1 

Get  the  specific  heat  of  either  copper  [use  bits  of 
wire];  lead  [use  100g  of  shot];  or  mercury  [use  100g  of 
mercury,  and  have  only  50g  of  water  in  the  calorim- 
eter]. 

The  discovery  made  by  Dulong  and  Petit  was  that, 
in  the  case  of  simple  substances,  the  greater  the  atomic 

1  See  foot-note,  page  xxvii  of  the  Introduction. 


208  THE   MODEEN   PERIOD. 

weight,  the  less  the  specific  heat ;  and  after  examining 
a  number  of  cases  they  concluded  that  it  could  be  stated 
as  a  law,  that,  if  the  specific  heat  of  a  simple  substance 
is  multiplied  by  the  weight  assigned  to  the  atom  of  that 
substance,  in  every  case  the  product  is  the  same  num- 
ber —  6  ± .  This  may  be  seen  by  inspecting  the  fol- 
lowing table  :  — 


SUBSTAXCE. 

Le&d.       .     .          • 

SPECIFIC 
HEAT. 

,     .       0.0314 

ATOMIC 
WEIGHT. 

207 

PRODUCT. 
6  5 

Mercury 

0.0333 

200 

6.7 

Antimony              . 

0.0508 

120 

6.1 

Silver 

.     .       0.0560 

108 

6.0 

Zinc        .     . 

,     .       0.0955 

65.3 

6.2 

Iron 

.     .       0.1138 

56 

6.4 

Phosphorus       .     .     , 

,     .       0.1887 

31 

5.8 

The  explanation  by  Dulong  and  Petit  for  these  facts 
was  that  every  atom  has  the  same  capacity  for  heat  that 
every  other  atom  has.  The  atom  of  lead  weighs  207mc, 
while  that  of  phosphorus  weighs  only  31mc;  and  the 
capacity  of  each  atom  for  heat  being  the  same,  the 
amount  of  heat  that  will  raise  31mc  [or  grams]  of 
phosphorus  one  degree,  will  raise  207mc  [or  granis] 
of  lead  one  degree  ;  hence  we  find  a  less  amount  of 
heat  required  to  raise  one  microcrith  [or  gram]  of  lead 
one  degree  than  to  raise  one  microcrith  [or  gram]  of 
phosphorus  one  degree.  And  this  is  what  the  above 
table  shows,  i.e.,  that  0.0314  calorie  will  raise  a  gram 
of  lead  one  degree,  while  it  requires  0.1887  calorie  to 
raise  a  gram  of  phosphorus  one  degree. 

In  other  words,  as  each  atom  of  lead  weighs  more 
than  each  atom  of  phosphorus,  there  would  foe>  in  equal 


LAW   OF    SPECIFIC    HEATS.  209 

amounts,  —  say,  ten  grams,  —  of  the  two  substances  a 
less  number  of  lead  atoms  than  of  phosphorus  atoms, 
and  therefore,  as  each  atom  requires  the  same  amount 
of  heat  to  heat  it  up  to  a  given  point,  a  less  amount  of 
heat  would  be  required  to  heat  up  the  ten  grams  of 
lead  than  the  ten  grams  of  phosphorus ;  or,  as  we  say, 
the  specific  heat  of  lead  is  less  than  the  specific  heat 
of  phosphorus.  Examine  the  table  and  note  that,  as 
the  specific  heats  increase,  the  atomic  weights  decrease, 
and  the  product  of  the  two  is  in  every  case  not  far 
from  six.  In  fact,  as  neither  the  specific  heats  nor 
the  atomic  weights  have  been  determined  with  perfect 
accuracy,  it  may  be  supposed  that  when  these  determi- 
nations shall  have  been  made  correctly  all  the  products 
will  be  the  same. 

The  discovery  of  this  relation  has  been  of  value  in  this 
way.  Suppose  you  have  found  the  combining  number 
for  copper  to  be  31.8,  and  you  wish  to  know  whether 
to  take  this  number  31.8,  or  2  times  31.8  =  63.6,  or  3 
times  31.8  =  95.4,  or  some  other  multiple  of  the  combin- 
ing number,  for  the  true  weight  of  the  atom.  Determine 
the  specific  heat  of  copper,  and  you  will  get  about  0.09. 

31.8  times  0.09  =  2.862 
63.6  «  0.09  =  5.724 
95.4  «  0.09  rr  8.586 

As  5.724  is  so  much  nearer  six  than  either  of  the  other 
numbers,  the  true  atomic  weight  of  copper  [if  the  law 
of  Dulong  and  Petit  is  to  be  trusted]  is  63.6.  After 
this  discovery  by  Dulong  and  Petit,  it  was  found  advis- 
able to  halve  the  values  of  several  atomic  weights  used 
up  to  that  time. 


210  THE   MODERN   PERIOD. 

Determine  the  true  atomic  weight  for  zinc  from 
its  combining-  number  and  its  specific  heat.  In  this 
determination  use  the  combining  number  and  the 
specific  heat  number  that  you  found  yourself. 

If  no  other  method  is  available,  even  the  atomic 
weight  itself  may  be  determined  from  the  specific  heat 
of  an  elementary  substance;  for  if  6.4,  which  is  a 
number  very  near  the  average  of  the  products  of  all 
reliable  atomic  weights  multiplied  by  the  corresponding 
specific  heats,  be  divided  by  the  known  specific  heat, 
the  required  atomic  weight,  or  a  number  very  near  to 
it,  will  be  obtained 

Though  a  help  in  determining  the  correct  atomic 
weights,  perfect  reliance  must  not  be  placed  on  this 
discovery  of  Dulong  and  Petit,  for  there  are  a  few 
substances,  e.g.,  carbon,  boron,  and  silicon,  the  pro- 
ducts of  whose  atomic  weights  multiplied  by  their 
specific  heats  [taken  at  ordinary  temperatures]  do  not 
equal  6  ±. 

For  Review.  —  §  12.  State  the  second  great  aid  that 
came  to  chemists  in  determining  which  multiple  of  the 
combining  number  to  take  for  the  true  atomic  weight. 
Who  discovered  this  aid  ?  When  ?  What  is  heat  sup- 
posed to  be?  Distinguish  between  temperature  and 
heat.  What  is  the  unit  amount  of  heat?  What  is 
this  unit  called?  What  is  a  calorimeter?  Define 
specific  heat.  Describe,  briefly,  a  method  for  finding 
the  specific  heat  of  a  metal.  When  tables  are  prepared 
showing  the  specific  heats  and  the  atomic  weights  of 
simple  substances  what  is  noticeable  ?  How  did  Dulong 


ISOMORPHISM.  211 

and  Petit  explain  this  peculiarity?  In  what  way  is  use 
made  of  the  relationship  between  specific  heat  and 
atomic  weight  ?  Show  how  you  can  tell,  by  means  of 
the  specific  heat,  the  best  multiple  of  the  combining 
number  for  zinc  to  choose  as  the  true  atomic  weight 
for  zinc. 


§  13.    ISOMORPHISM. 

Still  another  help  in  determining  atomic  weights  was 
found  in  the  discovery  of  a  relation  between  crystalline 
form  and  chemical  composition.  This  discovery  was 
made  by  a  German,  Mitscherlich,  who  announced,  just 
about  the  same  time  that  Dulong  and  Petit  made  their 
famous  discovery,  that  when  two  different  substances 
have  the  same  crystalline  form  their  isomorphism1  is 
due  to  the  fact  that  the  molecules  of  the  two  substances 
have  the  same  number  of  atoms,  and  that  these  atoms 
are  joined  in  the  same  way.  The  nature  of  the  atoms 
was  not  supposed  to  make  any  difference  whatever, 
i.e.,  one  substance  might  have  a  chlorine  atom  where 
another  had  a  bromine  atom,  but  there  must  be  the 
same  number  of  atoms. 


Experiment  32. 
Isomorphism. 

[a]  Take  a  small  amount  of  chloride  of  sodium ;  also 
a  little  iodide  of  sodium.  Recrystallize  each  from  a 
very  strong  and  very  hot  solution,  and  when  crystalliza- 


Isomorphism  means  a  similarity  of  form. 


212  THE   MODERN   PERIOD. 

tion  has  taken  place,  examine  [best  under  a  microscope 
of  low  power]  the  crystals  deposited.  What  is  the 
general  form  of  each? 

[b]  Repeat  the  experiment,  using  chloride  of  sodium 
and  chloride  of  potassium. 

Let  us  assume  that  we  know  chloride  of  sodium  is 
made  of  one  atom  of  chlorine  and  one  atom  of  sodium ; 
also  that  we  know  the  total  molecular  weight  of  the 
substance  to  be  58.5mc —  23mc  belonging  to  the  sodium 
and  35.5mc  belonging  to  the  chlorine.  Let  us  also 
assume  that  we  have  found  the  total  molecular  weight 
of  the  iodide  of  sodium  to  be  149. 9mc.  As  these  two 
substances  are  isomorphous,  they  must,  according  to  the 
law  of  Mitscherlich,  have  the  same  number  of  atoms, 
i.e.,  the  iodide  must  have  one  atom  of  iodine  and  one 
of  sodium.  As  the  total  weight  of  the  two  atoms  is 
149.9,  and  the  sodium  weighs  23,  iodine  must  have 
an  atomic  weight  of  149.9  —  23.  =  126.9. 

Assuming  that  we  have  found  the  molecular  weight 
of  chloride  of  'potassium  to  be  74.6,  find,  by  the  prin- 
ciple of  isomorphism,  the  atomic  weight  of  potassium. 

Though  this  discovery  by  Mitscherlich  has  been  a 
valuable  aid,  later  investigations  have  shown  that  it 
cannot  be  relied  upon,  for  there  are  some  substances, 
e.g.,  sodium  sulphate  and  barium  manganate,  which 
crystallize  in  the  same  form,  but  do  not  have  a  similar 
composition. 

For  Review.  —  §  13.  What  was  the  third  great  aid 
that  came  to  chemists  in  determining  which  multiple 
of  the  combining  number  for  an  element  should  be 
taken  as  its  true  atomic  weight?  Who  discovered 


THE   PERIODIC    LAW.  213 

this  aid?    What  is  isomorphism?    Give  an  illustration. 
Why  can  not  this  method  be  relied  upon  ? 


§  14.     PERIODIC  LAW. 

The  last  discovery  of  importance  which  helps  us  in 
determining  atomic  weights  is  the  law  of  periodicity. 
In  1864,  Newlands,  an  English  chemist,  made  an  ar- 
rangement of  the  elements  according  to  their  atomic 
weights.  He  called  attention  to  the  fact  that,  when 
thus  arranged  in  form  of  a  table,  the  elements  fall  into 
natural  groups,  each  group  distinguished  by  its  members 
having  similar  properties.  Not  much  serious  attention 
was  paid  to  this  table  of  Newlands.  He  was  even  asked, 
jokingly,  if  he  would  not  next  prepare  a  table  of 
elements  arranged  according  to  the  first  letters  of  their 
names,  and  see  if  he  could  not  get  similar  groups.  But, 
nevertheless,  this  classification  by  Newlands  contained 
the  germ  of  an  important  discovery. 

In  1869,1  Lothar  Meyer,  a  German  chemist,  published 
a  classification  of  the  elements  far  more  extended  and 
better  arranged  than  Newlands'.  He  found  that  if  the 
elements  are  written  in  lines  from  left  to  right  accord- 
ing to  their  increasing  atomic  weights,  that  [excluding 
hydrogen,  the  lowest  in  weight,  and  beginning  with 
lithium],  when  the  eighth,  sodium,  is  reached,  it  much 
resembles  lithium,  the  first;  and  the  ninth  resembles 
the  second ;  and,  again,  the  fifteenth,  potassium,  re- 
sembles lithium,  the  first ;  and  the  sixteenth  resembles 

1  About  the  same  time  Mendele'eff:,  a  Russian  chemist,  called  atten- 
tion to  the  fact  that  he  also  had  come  to  the  conclusion  that  there  was 
a  great  law  underlying  these  same  facts. 


214  THE   MODEKN   PERIOD. 

the  ninth.  Meyer  arranged  a  table  showing  clearly 
this  periodic  recurrence  of  similar  properties.  There 
were  a  number  of  vacant  places  in  the  table,  but  it  was 
suggested  that  these  might  be  filled  by  elements  not 
discovered. 

A  study  of  this  table  shows  that  elements  whose  prop- 
erties are  similar  may  be  grouped  in  natural  families, 
among  the  members  of  which  there  is  a  regular  increase 
in  the  atomic  weights,  and  a  corresponding  progressive 
change  in  both  physical  and  chemical  properties. 

Since  1870  much  attention  has  been  given  to  the 
development  of  this  table,  and,  in  general,  all  observa- 
tions have  gone  to  prove  that  the  properties  of  any  ele- 
ment are  periodic  functions  of  its  atomic  weight;  or,  in 
other  words,  the  properties  of  elements  vary  as  their 
atomic  weights  change.  This  is  called  The  Periodic 
Law,  with  which  the  name  of  Mendele'eff  is  so  often 
associated. 

To  understand  the  grounds  on  which  the  law  is  based 
one  must  have  an  intimate  knowledge  of  both  physical 
and  chemical  properties,  as  well  as  of  the  atomic  weights, 
of  all  the  elements  —  a  knowledge  that  can  scarcely  be 
obtained  in  a  year  [or  perhaps  years]  of  chemical  study.1 
Hence  we  shall  make  no  attempt  at  doing  any  experi- 
ments to  illustrate  the  periodic  law. 

The  use  made  of  the  periodic  law  in  determining 
atomic  weights  is  as  follows :  If  the  properties  of  an 
elementary  substance  are  known,  the  substance  can  be 

1  The  author  advises  a  student  who  can  spend  a  second  year  on 
chemistry  to  devote  his  second  year  to  Descriptive  Chemistry,  i.e., 
largely  to  a  study  of  properties  of  substances,  rather  than  to  Qualita- 
tive Analysis. 


THE   PERIODIC   LAW. 


215 


fitted  into  the  periodic  table  among  elements  of  similar 
properties,  and,  from  its  position,  its  probable  atomic 
weight  can  be  inferred. 

It  is  of  interest  to  note  how  one  of  the  gaps  in 
the  periodic  table  has  been  filled.  Mendele'eff  himself 
predicted  that  there  was  an  element  [missing]  whose 
atomic  weight  was  72.  From  the  properties  of  its 
neighbors  in  the  table  he  ventured  to  predict  the  proper- 
ties of  this  missing  element.  In  1886  Clemens  Winkler 
discovered  a  new  element  whose  atomic  weight  has  been 
determined  as  72.3.  Let  us  look  at  the  properties  as 
predicted  by  Mendele'eff:  and  those  found  by  Winkler. 

FOUND. 

Atomic  weight,  72.3. 
Specific  gravity,  5.49. 
Forms  an  oxide  when  heated 
in  the  air. 


PREDICTED. 

Atomic  weight,  72. 

Specific  gravity,  5.5. 

Will  form  an  oxide  when  heated 
in  the  air. 

Oxide  will  have  two  atoms  of 
oxygen. 

Easily  obtained  from  its  ore 
by  reduction  with  carbon  or 
sodium. 

A  metal. 

Dirty  grey. 

Will  melt  with  difficulty. 

Will  form  a  chloride  with  four 
atoms  of  chlorine. 

Chloride  will  boil  near  100°, 
probably  lower. 

Will  form  a  sulphide. 

Sulphide  will  not  be  soluble  in 
water,  but  probably  will  dis- 
solve in  sulphide  of  ammo- 
nium. 

Scarcely  acted  on  by  acids. 


Two  atoms  of  oxygen  in  the 

oxide. 
Easily  obtained   from   its   ore 

by  reduction  with  carbon  or 

hydrogen. 
A  metal. 
Grey-white. 
Melts  at  900°  C. 
Forms    a    chloride   which   has 

foui*  atoms  of  chlorine. 
Chloride  boils  at  86°. 

Forms  a  sulphide. 

Sulphide  is  moderately  soluble 
in  water,  more  readily  in  sul- 
phide of  ammonium. 

Not  acted  on  by  acids. 


216 


THE   MODEBN  PEEIOD. 


There  are  at  present  seventy-two  elements  recognized. 
All  the  aids  we  have  for  the  determination  of  their 
atomic  weights  have  been  brought  to  bear,  and  many 
skilful  workers  have  devoted  years  of  time  and  thought, 
and  are  still  devoting  time  and  thought,  to  the  accu- 
rate determination  of  the  relative  weights  of  the  atoms. 
Still  the  work  is  by  no  means  satisfactorily  completed. 
Below  is  given  a  list l  of  the  seventy-two  elements,  and 
the  weights  now  assigned  to  them.  The  figures  are 
not  given  [though  in  many  cases  determined]  beyond 
the  first  place  of  decimals. 


Aluminum, 

27.1 

Germanium,     72.3 

Phosphorus, 

31. 

Antimony, 

120. 

Glucinum,           9.1 

Platinum, 

195. 

Arsenic, 

75. 

Gold,               1*97.3 

Potassium, 

39.1 

Barium, 

137.4 

Hydrogen,           1. 

Praseodimium, 

144.5 

Bismuth, 

208. 

Indium,           113.7 

Rhodium, 

103. 

Boron, 

11. 

Iodine,             126.9 

Rhubidium, 

85.4 

Bromine, 

79.9 

Iridium,          193. 

Ruthenium, 

101.6 

Cadmium, 

112.2 

Iron,                  56. 

Samarium, 

150.? 

Caesium, 

132.9 

Lanthanum,   13.8.2 

Scandium, 

44. 

Calcium, 

40. 

Lead,              206.9 

Selenium, 

79. 

Carbon, 

12. 

Lithium,             7. 

Silicon, 

28.4 

Cerium, 

140.2 

Magnesium,     24.4 

Silver, 

107.9 

Chlorine, 

35.5 

Manganese,      55.1 

Sodium, 

23. 

Chromium, 

52.1 

Mercury,         200. 

Strontium, 

87.6 

Cobalt, 

59. 

Molybdenum,  96. 

Sulphur, 

32.1 

Columbium, 

94. 

Neodymium,  141. 

Tantalum, 

182.5 

Copper, 

63.6 

Nickel,             58.6 

Tellurium, 

125. 

Erbium, 

166.? 

Nitrogen,          14. 

Terbium, 

160.? 

Fluorine, 

19. 

Osmium,         190.8 

Thallium, 

204.2 

Gadolinium, 

156.1 

Oxygen,            16. 

Thorium, 

233.1 

Gallium, 

70. 

Palladium,     106.6 

Thulium, 

171.? 

1  Taken  from  a  recent  revision  by  Dr.  Richards  of  Harvard  Uni- 
versity. 


MODERN  ATOMIC   WEIGHTS.  217 

Tin,  119.  Uranium,       240.  Yttrium,          89.? 

Titanium,        48.1.         Vanadium,      51.3          Zinc,  65.3 

Tungsten,      184.  Ytterbium,     173.  Zirconium,       90.6 

For  Review.  — 14.  What  is  the  fourth  and  last 
great  aid  that  has  come  to  help  in  the  determination 
of  atomic  weights?  State  briefly  the  history  of  the 
discovery  of  this  aid.  What  is  meant  by  the  periodic 
law  ?  How  has  this  law  been  used  with  success  ? 

How  many  elements  are  now  recognized?  Fix  in 
mind  the  atomic  weights  now  assigned  to  those  atoms 
in  which  you  feel  the  most  interest. 


218  LANGUAGE   OF   CHEMISTRY. 


LANGUAGE   OF   CHEMISTRY. 

The  language  of  chemistry  is  largely  symbolical.  It 
is  a  kind  of  shorthand,  combinations  of  letters  and 
figures  being  used  to  represent  the  names  of  substances, 
and  signs  to  express  processes. 

The  first  letter  [or  the  first  and  some  other  prominent 
letter]  of  the  Latin  name  of  an  element  is  used  as  the 
symbol  for  that  element.  Thus,  H  represents  an  atom 
of  hydrogen  ;  O,  an  atom  of  oxygen  ;  S,  an  atom  of  sul- 
phur ;  C,  an  atom  of  carbon ;  Ca,  an  atom  of  calcium ; 
Cl,  an  atom  of  chlorine.  Of  course  if  C  has  been  taken 
to  represent  the  atom  of  carbon  it  cannot  also  stand  for 
the  atom  of  calcium,  hence  Ca,  the  first  letter  and 
another  prominent  letter,  are  taken  for  the  symbol.  In 
the  same  way,  to  represent  chlorine,  Cl  is  used. 

In  most  cases  the  English  and  the  Latin  names 
begin  with  the  same  letters.  The  following  are  the 
exceptions :  — 

ENGLISH.  LATIN.  SYMBOL. 

Antimony      ....  Stibium Sb 

Gold Aurum Au 

Iron Ferrum Fe 

Lead Plumbum Pb 

Mercury Hydrargyrum     ....  Hg 

Potassium     ....  Kalium K 

Silver Argentum Ag 

Sodium Natrium Na, 

Tin Stannum Sn 

Tungsten      ....  Wolframium W 


LANGUAGE   OF   CHEMISTRY. 


219 


The  following  is  a  complete  list  of  the  symbols  of 
the  seventy-two  elements : 


SYMBOL.        NAME.           SYMBOL. 

NAME. 

SYMBOL. 

.  Al 

Hydrogen    .     .  H 

Ruthenium. 

.  Ru 

.  Sb 

Indium  ...  In 

Samarium  . 

.  Sm 

.  As 

Iodine     ...  I 

Scandium   . 

.  Sc 

.  Ba 

Iridium  .     .     .  Ir 

Selenium    . 

.  Se 

.  Bi 

Iron    .     .     .     .  Fe 

Silicon    .     . 

.  Si 

.  B 

Lanthanum      .  La 

Silver     .     . 

•  Ag 

.  Br 

Lead  .     .     .     .  Pb 

Sodium  .     . 

.  Na 

.  Cd 

Lithium  ...  Li 

Strontium  . 

.  Sr 

.  Cs 

Magnesium.     .  Mg 

Sulphur.     . 

.  S 

.  Ca 

Manganese  .     .  Mn 

Tantalum  . 

.  Ta 

.  C 

Mercury  .     .     .  Hg 

Tellurium  . 

.  Te 

.  Ce 

Molybdenum    .  Mo 

Terbium     . 

.  Tb 

.  Cl 

Neodymium      .  Nd 

Thallium   . 

.  Tl 

.  Cr 

Nickel     .     .     .  Ni 

Thorium    . 

.  Th 

.  Co 

Nitrogen      .     .  N 

Thulium    . 

.  Tu 

.  Cb 

Osmium.     .     .  Os 

Tin  .    ..  V 

.  Sn 

.  Cu 

Oxygen  .     .     .  O 

Titanium  . 

.  Ti 

.  Er 

Palladium   .     .  Pd 

Tungsten  . 

.  W 

.  F 

Phosphorus.     .  P 

Uranium    . 

.  U 

.  Gd 

Platinum     .     .  Pt 

Vanadium. 

.  V 

.  Ga 

Potassium  .     .  K 

Ytterbium. 

.  Yb 

.  Ge 

Praseodymium,  Pr 

Yttrium     . 

.  Yt 

.  Gl 

Rhodium     .     .  Rh 

Zinc  . 

.  Zn 

.  Au 

Rhubidium.     .  Rb 

Zirconium  . 

.  Zr 

NAME. 
Aluminum 
Antimony 
Arsenic     . 
Barium     . 
Bismuth    . 
Boron  .     . 
Bromine    . 
Cadmium . 
Caesium    . 
Calcium    . 
Carbon 
Cerium 
Chlorine    . 
Chromium 
Cobalt  .     . 
Columbium 
Copper .     . 
Erbium     . 
Fluorine    . 
Gadolinium 
Gallium    . 
Germanium 
Glucinum . 
Gold 


The  atomic  weight  of  an  element  should  always  be 
associated  with  its  symbol,  thus,  H  should  represent  to 
your  mind  lmc  of  hydrogen ;  C,  12mc  of  carbon ;  Fe,  56mc 
of  iron ;  Zn,  65.3mc  of  zinc,  and  so  on. 

To  express  compounds  there  are  used  symbols  called 
formulae,  made  by  writing  together  the  symbols  of  the 
atoms  that  are  in  the  molecule  of  the  compound,  thus, 


220  LANGUAGE   OF   CHEMISTRY. 

HC1  is 'the  formula  for  a  molecule  of  hydrochloric  acid; 
NaOH  represents  a  molecule  of  hydroxide  of  sodium. 
When  there  are  several  atoms  of  the  same  kind  in  the 
molecule  subnumerals  are  used,  thus,  H2O  stands  for  a 
molecule  of  water;  HNO3,  for  one  of  nitric  acid;  H2, 
for  a  molecule  of  hydrogen  gas ;  O2,  for  a  molecule  of 
oxygen  gas ;  CaCO3,  for  one  of  carbonate  of  calcium ; 
NH3,  for  one  of  .ammonia;  and  H2SO4,  for  one  of 
sulphuric  acid. 

If  the  symbol  for  every  atom  has  the  correct  atomic 
weight  associated  with  it,  there  is  no  difficulty  in  tell- 
ing the  molecular  weight  of  a  substance  if  its  formula 
is  known,  for  the  molecular  weight  must  be  the  sum  of 
the  weights  of  all  the  atoms  that  go  to  make  up  the 
molecule.  What,  then,  is  the  molecular  weight  of 
hydrochloric  acid?  Of  carbonate  of  calcium?  Of 
sulphuric  acid? 

The  formula  of  a  molecule  always  tells  three  things: 
first,  what  the  substance  is  ;  second,  of  what  atoms  it  is 
composed ;  third,  what  the  molecular  weight  is. 

To  express  two  or  more  molecules,  or  atoms,  coeffi- 
cients are  used.  Thus,  2  H2O  represents  two  molecules 
of  water;  5  H2SO4  stands  for  five  molecules  of  sul- 
phuric acid;  10  K2SO4,  for  ten  molecules  of  sulphate  of 
potassium ;  2  H,  for  two  atoms  of  hydrogen ;  2  H2,  for 
two  molecules  of  hydrogen ;  7  NaCl,  for  seven  molecules 
of  common  salt ;  3  O,  for  three  atoms  of  oxygen ;  3  O2, 
for  three  molecules  of  oxygen;  and  3  O3,  for  three 
molecules  of  ozone — a  substance  we  have  not  studied. 

Note.  Be  sure  that  you  see  the  distinction  between 
atomic  and  molecular  expressions.  State  which  of  the 


LANGUAGE   OF   CHEMISTRY.  221 

following  are  atomic  and  which  molecular :  H,  H2,  7  H, 
2  H,  5  C12,  HC1,  H2O,  H2O2,  3  O. 

In  chemistry  the  action  of  one  substance  on  another 
is  represented  by  the  sign  +,  and  equations  are  used  to 
express  chemical  changes,  the  factors  of  the  change 
being  put  before  the  sign  — ,  and  the  products  after. 
Thus,  ZnO  +  H2SO4  =  ZnSO4  +  H2O,  represents  the 
change  that  takes  place  when  the  oxide  of  zinc  acts  on 
sulphuric  acid.  When  water  is  used  simply  to  produce 
solution,  the  symbol  Aq,  standing  for  the  Latin  word 
aqua,  is  used.  Thus  the  reaction  of  ZnO  and  H2SO4, 
as  we  conducted  it,  would  be  represented  as  follows: 
ZnO  +  [H2S04  +  Aq]  =  [ZnS04  +  H2O  +  Aq].  The 
brackets  are  used  to  indicate  the  solutions.  As  the  Aq 
seems  to  play  no  part  chemically  in  the  changes,  this 
symbol  is  frequently  omitted  altogether.  The  neutral- 
ization of  hydrochloric  acid  with  hydroxide  of  potassium 
is  represented  thus :  HC1  +  KOH  =  KC1  +  H2O  ;  and 
the  neutralization  of  sulphuric  acid  with  hydroxide  of 
sodium  thus :  H2SO4  +  2  NaOH  =  Na2SO4  +  2  H2O. 

Write  in  equation  form  the  changes  that  were 
brought  about  : 

[a]  When  an  atom  of  zinc  acted  on  a  molecule  of 
sulphuric  acid  in  water  solution ; 

[6]  When  oxygen  and  hydrogen  gases  were  pro- 
duced from  water  by  the  electric  current.  It  will 
not  do  to  write  this  H2O  =  H2  +  O,  because  molecules 
of  oxygen  gas  came  bubbling  up.  The  equation 
should  be  written,  2  H2O  =  2  H2  +  O2; 

[<?]    When  oxygen,  was  made  by  heating  the  chlorate 


222  LANGUAGE   OF   CHEMISTRY. 

of  potassium.  Here  assume,  as  in  the  last  case,  that 
the  gas  came  off  in  molecules.  The  formula  for  a 
molecule  of  chlorate  of  potassium  is  KC1O3,  and  that 
for  the  chloride  which  results  is  KC1; 

[d]  When  oxygen  gas  acted  on  phosphorus.     The 
formula  for  a  molecule  of  phosphorus  is  P4,  and  that 
for  the  resulting  white  oxide  is  P2O5 ; 

[e]  When   an   atom   of  carbon  burned  in   oxygen, 
producing  the  dioxide  of  carbon,  CO2; 

[/]  When  an  atom  of  sulphur  burned  in  oxygen, 
producing  the  dioxide  of  sulphur,  SO2; 

\_g~\  When  a  molecule  of  water  was  added  to  a 
molecule  of  dioxide  of  sulphur,  and  there  resulted  a 
molecule  of  sulphurous  acid,  H2SO3; 

[h]  When  O2  and  SO2  were  passed  over  hot  plati- 
num sponge,  and  SO3 — the  second  oxide  of  sulphur — 
resulted ; 

[i]  When  sulphuric  acid — H2SO4 — was  produced 
by  the  addition  of  water  to  the  second  oxide  of  sulphur ; 

[j]  When  two  molecules  of  HC1,  in  water  solution, 
reacted  with  one  molecule  of  carbonate  of  calcium, 
CaC03; 

[Jc]  When  five  volumes  of  H2  acted  with  two  vol- 
umes of  NO,  and  there  resulted  two  volumes  of  ammo- 
nia— NH3 — and  two  volumes  of  steam. 

Note  that  these  chemical  equations  are  nothing  more 
than  a  short  way  of  expressing  chemical  facts.  They 
resemble  algebraic  equations,  inasmuch  as  there  are  the 
same  atoms  on  one  side  of  the  sign  of  equality  that 
there  are  on  the  other  side ;  and,  consequently,  the  sum 


LANGUAGE   OF   CHEMISTRY.  223 

of  the  atomic  weights  on  one  side  equals  the  sum  of 
those  on  the  other.  But  it  is  not  true  that  any  trans- 
position that  can  be  made  in  algebra  can  be  made  in  a 
chemical  equation.  Chemical  equations  are  far  less 
flexible  than  algebraic  ones,  the  chemical  being  limited 
to  the  expression  of  observed  facts.  This  is  an  impor- 
tant point,  and  should  not  be  forgotten. 

A  chemical  equation  always  expresses  two  of  the 
great  laws  of  chemistry,  and,  when  gaseous  substances 
are  involved,  it  expresses  a  third.  It  always  expresses 
the  law  of  conservation  of  mass,  as  is  shown  by  the  use 
of  the  equality  sign.  It  also  always  expresses  the  law 
of  definite  proportions  by  weight,  because  the  symbols 
used  stand  for  definite  weights  of  matter.  And,  when 
any  of  the  substances  are  gases,  the  simple  ratio  between 
their  coefficients  expresses  the  law  of  definite  propor- 
tions by  volume. 

Note,  that,  in  addition  to  the  three  facts  [see  page  220] 
that  the  formula  for  a  molecule  always  expresses,  there 
is  a  fourth  shown  when  the  formula  is  that  of  a  gaseous 
substance.  The  simple  molecular  formulae  of  gases  all 
represent  the  same  volume.  O2,  H2,  C12,  N2,  H2O 
[steam],  NH3,  NO,  NO2,  CO2,  SO^  CO,  and  HC1  all 
represent  the  same  volume ;  for,  according  to  the 
hypothesis  of  Avogadro  that  in  equal  volumes  of  all 
gases  there  are  the  same  number  of  molecules,  it 
follows  that  every  molecule  occupies  just  as  much 
space  as  every  other  molecule.  Hence  the  formula 
for  the  molecule  of  any  gaseous  substance  represents 
a  definite  volume  of  that  substance.  * 


224  STOICHIOMETEY. 


STOICHIOMETRY. 

If  we  know  the  equation  that  expresses  any  chemical 
change  and  know  the  weight  in  grams  of  a  single  sub- 
stance that  enters  into  the  change  we  can  calculate  the 
weight  of  every  other  substance  involved.  This  power 
to  calculate  unknown  weights  of  substances  is  one  of 
great  value  to  the  chemist.  If,  for  instance,  he  is  called 
upon  to  produce  100  grams  of  silver  chloride,  it  is  not 
necessary  for  him,  as  it  was  in  the  old  days,  to  guess  at 
the  amounts  of  nitrate  of  silver  and  of  common  salt  to 
use,  with  a  good  chance  of  making  just  a  little  less  than 
the  ten  grams  or  a  considerable  amount  more,  nor  need 
he  go  "  by  rule  of  thumb."  By  the  aid  of  a  chemical 
equation  and  his  knowledge  of  the  atomic  weights  he 
can  calculate  the  exact  amounts  of  the  factors  required 
to  yield  the  required  weight  of  product.  Let  us  make 
the  calculation.  First  write  the  equation  expressing  the 
change.  It  is  this :  AgNO3  +  NaCl  =  AgCl  +  NaNO3. 
Now  write  above  the  formula  for  each  molecule  its  mo- 
lecular weight,  i.e.,  the  sum  of  the  weights  of  all  the 
atoms  in  the  molecule.  As  the  weights,  in  grams  [or 
in  pounds,  or  in  terms  of  any  other  unit],  bear  to  each 
other  the  same  ratio  as  do  the  molecular  weights,  pro- 
portions can  be  made  enabling  us  to  find  the  unknown 
amounts,  e.g.,  the  molecular  weight  of  the  AgCl  is  to 
the  molecular  Weight  of  the  AgNO3,  as  is  the  gram 
weight  of  AgCl  [known  to  be  10]  to  the  gram  weight 
ofAgNO3,  or  143.5: 170::  10  :z.  x=UM -.  There- 
fore. ll.$5g  of  nitrate  of  silver  will  be  required  to 


STOICHIOMETRY..  225 

produce  10g  of  chloride  of  silver.  Now  calculate  how 
much  NaCl  is  needed.  Also  calculate  the  weight  of 
the  nitrate  of  sodium  that  will  also  result  from  the 
change.  See  if  the  sum  of  the  weights  of  the  products 
equals  the  sum  of  the  weights  of  the  factors.  This 
finding  of  unknown  amounts  is  called  stoichiometry. 

The  chief  rule  of  stoichiometry  is  as  follows :  When 
the  gram  weight  of  one  substance  which  is  involved  in 
a  chemical  change  is  known,  in  order  to  find  the  gram 
weight  of  any  other  substance  involved,  make  a  pro- 
portion thus :  the  molecular  weight  of  the  known  is  to  the 
molecular  weight  of  the  unknown  as  the  gram  weight  of  the 
known  is  to  x.  x  will  be  the  required  gram  weight. 

If  it  is  desired  to  find  the  volume  of  a  gas  that  will 
be  produced  in  a  given  case,  first  find  the  weight  of 
gas  produced :  then  calculate  [making  use  of  the  known 
density  of  the  given  gas]  the  volume  this  weight  would 
occupy  at  N.  T.  P. :  and,  finally,  calculate  [using  the 
laws  of  Boyle  and  of  Daltoii]  the  volume  which  this 
volume  at  N.  T.  P.  will  occupy  under  the  given  con- 
ditions, 


226  MANIPULATIONS. 


MANIPULATIONS. 

The  following  directions  may  be  of  service  in  per- 
forming the  mechanical  operations  that  so  often  occur 
in  laboratory  practice : 

To  Mark  Glass. 

This  can  best  be  done  with  a  pencil  that  has  recently 
been  invented  for  the  purpose.  Each  student  should 
keep  one  of  these  pencils  constantly  at  hand  in  his 
desk.  By  its  frequent  use,  particularly  in  marking 
the  point  at  which  tubes  are  to  be  cut,  and  in  labelling 
vessels  that  have  to  be  set  away  at  the  end  of  labora- 
tory periods,  much  time  and  annoyance  will  be  saved. 
These  pencils  may  be  obtained  from  the  publishers  of 
this  book  —  Ginn  and  Company. 

To  Cut  Glass. 

Small  and  medium  tubes,  and  rods,  are  best  cut  as 
follows :  With  a  sharp  triangular  file  make  a  short 
scratch  at  the  point  where  the  tube  is  to  be  cut.  Take 
the  tube  in  your  hands  with  the  two  thumbs  on  the 
tube  under  the  scratch,  and  the  fingers  of  each  hand 
spread  out  on  the  tube  to  the  right  and  the  left  of 
the  scratch.  The  nails  of  the  two  thumbs  should  be 
close  together  and  touching  the  glass  exactly  under  the 
scratch.  By  means  of  the  two  little  fingers  bring  a 
gradually  increasing  downward  pressure  to  bear,  letting 
the  thumb  nails  act  as  a  fulcrum. 


MANIPULATIONS.  227 

Larger  tubes,  e.g.,  combustion  tubes  one  or  more 
cm  in  diameter,  may  be  cut  in  a  similar  manner  by 
substituting  the  edge  of  a  triangular  file,  resting  on 
the  desk,  for  the  fulcrum,  and  pressing  downward  with 
the  palms  of  the  two  hands.  If,  however,  the  tube  to 
be  cut  is  very  short,  proceed  thus  :  Make  the  scratch 
with  the  file,  then  either  touch  this  scratch  suddenly 
with  a  hot  iron,  e.g.,  the  end  of  an  old  file  heated  red- 
hot  in  the  Bunsen  flame  ;  or  drop  upon  it  a  bead  of 
red-hot  molten  glass  ;  or,  best  of  all,  apply  to  it  a  small 
gas-flame,  which  may  be  made  by  disconnecting  the 
Bunsen  burner  from  its  tube  and  inserting  in  the  end 
of  the  tube  a  tip  of  hard  glass  drawn  out  like  the  wash- 
bottle  tip.  The  best  flame  is  a  vigorous,  clear-cut, 
smokeless  one,  about  lcm  long,  produced  by  a  small 
opening  and  a  full  pressure  of  gas.  When  such  a 
flame  is  applied  to  the  scratch  the  tube  usually  snaps 
square  off.  If  it  does  not  snap  within  half  a  minute, 
the  change  of  temperature  has  not  been  sudden  enough. 
Cool  the  tube,  and  apply  the  flame  again.  If  a  crack 
starts  but  does  not  run  entirely  around,  or  does  not  run 
straight,  turn  off  the  gas  till  the  flame  is  only  about 
2mm  long,  and  apply  this  flame  to  the  glass  just  beyond 
the  end  of  the  crack.  The  crack  will  advance  to  the 
flame.  Move  the  flame  ahead,  and  in  this  way  lead 
the  crack  around  wherever  you  wish. 

To  cut  off  the  necks  of  bottles,  beakers,  and  test- 
tubes,  make  a  scratch  with  a  file,  and  start  a  crack  as 
directed  above.  Lead  this  crack,  best  with  the  2mm 
flame,  around  the  neck  of  the  vessel.  In  this  way 
chipped  or  cracked  beakers  and  test-tubes  may  often 


228  MANIPULATIONS. 

be  made  into  serviceable  articles,  by  cutting  off  their 
tops  and  fire-polishing  the  sharp  edges. 

To  Fire-polish  the  Edges  of  Glassware. 

All  sharp  glass  edges,  e.g.,  ends  of  tubes  and  rods, 
freshly  cut  necks  of  bottles,  broken  edges  of  beakers 
and  test-tubes,  should  be  melted  in  the  Bunsen  flame 
till  they  are  smooth  and  rounded.  The  flame  of  the 
Bunsen  burner  is  usually  sufficient,  but  the  work  can 
be  done  quicker  in  the  flame  of  the  blast-lamp.  Great 
care  must  be  taken,  particularly  with  the  latter  flame, 
not  to  crack  the  glass  by  too  sudden  application  of  the 
heat.  Begin  with  a  small  flame,  which  must  be  in- 
creased slowly.  When  heating  glass  there  is  less 
danger  of  its  snapping  if  it  is  immersed  first  in  the 
less  vigorous,  luminous,  sooty  flame,  and  heated  as  hot 
as  possible  there  before  it  is  put  in  the  Bunsen  flame. 
In  the  case  of  thick  glass  the  article  should  not  at  first 
be  held  continuously,  even  in  the  luminous  flame,  but 
should  be  immersed  for  a  moment,  then  withdrawn 
for  a  moment,  again  immersed,  and  so  on,  till  it  is 
thoroughly  heated.  Thick  glass  is  more  apt  than  thin 
to  crack  by  a  sudden  application  of  heat,  because  the 
side  where  the  heat  is  applied  expands  before  the  heat 
has  passed  to  the  other  side  and  expanded  that, — 
hence  a  rupture. 

To  Bend  Glass  Tubes  and  Rods. 

This  must  be  done  in  a  wide  flame,  and  not  in  the 
common  Bunsen  burner  flame,  and,  except  in  the  case 
of  very  short  tubes,  not  in  the  blast-lamp  flame.  A 


MANIPULATIONS.  229 

common  bat-wing  gas  jet  [used  for  illuminating  pur- 
poses] is  good,  but  leaves  the  tube  sooty.  Better 
than  this  is  the  broad  tip  furnished  for  this  purpose 
with  some  Bunsen  burners. 

Hold  the  tube,  at  the  point  where  it  is  to  be  bent,  in 
the  hottest  part  of  the  broad  flame.  In  the  case  of  an 
ordinary  tube,  a  length  of  at  least  6cm  should  be  im- 
mersed in  the  flame.  Turn  the  tube  slowly,  so  that  all 
sides  shall  be  equally  heated.  When  the  tube  has 
softened,  and  you  feel  it  to  be  flexible,  remove  it  from 
the  flame,  and  quickly,  but  deliberately,  bend  it  to  the 
exact  angle  wanted.  If  the  right  angle  is  not  obtained 
at  the  first  attempt,  it  is  hardly  worth  while  to  heat 
again  and  try  to  bend  it  into  shape.  Better  take  a 
new  piece  of  glass  and  start  again. 

To  Draw  Out  Glass  Tubes. 

Begin  as  directed  for  bending  tubes,  but  heat  more. 
When  the  glass  has  softened  so  much  that  it  begins  to 
sag,  remove  it  from  the  flame  and  draw  it  to  the  shape 
wished.  Wash-bottle  tips,  and  the  like,  may  be  made 
either  with  the  bat-wing  flame  or  in  the  Bunsen  burner 
flame.  Large  or  very  hard  tubes  best  be  drawn  with 
the  aid  of  the  blast-lamp.  In  using  the  blasi^lamp  for 
this  purpose  care  should  be  taken  to  apply  the  heat 
gradually,  as  directed  under  fire-polishing.  When  it  is 
desired  to  draw  out  a  long  length  of  capillary  tube, 
the  glass  should  be  made  very  soft,  removed  from  the 
flame,  drawn  to  the  right  diameter,  allowed  to  cool  a  few 
seconds  in  order  to  take  a  " set"  and  then  rapidly  drawn 
to  obtain  length. 


230  MANIPULATIONS. 


To  Make  a  Matrass. 

A  matrass  is  a  hard  glass  vessel  with  a  long  slim  neck 
and  a  bulb-like  body.  For  a  large  matrass  a  Kjeldahl 
flask  serves  excellently.  Small  matrasses,  often  called 
"bulb-tubes,"  are  frequently  used  when  a  substance  has 
to  be  heated  in  a  flame  so  hot  that  it  would  soften  an 
ordinary  test-tube. 

To  make  a  small  matrass  :  Take  a  piece  of  hard  glass 
tube  of  5-1  Omm  bore.  Hold  one  end  in  the  blast-lamp 
flame  till  the  glass  is  soft.  With  the  forceps  pinch  the 
softened  walls  together,  and  quickly  draw  off,  and  reject, 
about  lcm  of  the  end  of  the  tube.  Immerse  the  closed 
end  of  the  tube  in  the  blast-lamp  flame  ;  hold  it  there 
till  a  lump  of  softened  glass  has  collected ;  then  put 
the  open  end  in  your  mouth  and  blow  gently  till  the 
lump  of  glass  forms  a  bulb. 

To  Render  Corks  Air-tight.1 

Melt  some  solid  paraffine  —  a  candle  will  do  —  in  a 
dipper.  Roll  the  cork  a  little  under  the  foot,  and 
then  soak  it  for  a  few  minutes  in  the  melted  paraffine. 
Never  attempt  to  tighten  leaky  joints  by  applying  par- 
affine, sealing-wax,  etc.  This  application  is  not  worth 
the  trouble,  seldom  stops  the  leak,  and  looks  shiftless, 
as  apparatus  properly  constructed  never  needs  any  such 
doctoring. 

1  Good  corks  need  no  treatment,  but  in  a  gross  of  corks  it  is  seldom 
that  there  are  not  a  number  which  are  not  air-tight. 


MANIPULATIONS.  231 


To  Render  Joints  Air-tight. 

Before  putting  stoppers  in  the  necks  of  bottles, 
rubber  bands  on  jars,  rubber  hose  on  tubes,  etc.,  the 
surfaces  of  contact  should  be  greased,  if  an  air-tight 
joint  is  wanted.  Vaseline  makes  an  excellent  grease. 

To  Cut  Rubber  Neatly  and  Quickly. 

Use  a  sharp  knife,  and  keep  the  cut  wet.  A  small 
oil-stone  should  be  kept  at  hand  in  the  laboratory  for 
sharpening  knives. 

To  Pass  a  Glass  Tube  Through  a  Hole  in  a 
Rubber  Stopper. 

Apply  vaseline  or  glycerine  to  the  glass.  In  this 
way  a  tube  that  seems  too  big  for  the  hole  may  be 
slipped  through  easily,  particularly  if  its  end  has  been 
fire-polished. 

To  Bore  a  Round  Hole  in  Glass. 

It  is  often  desirable  to  make  a  hole  in  the  side  of  a 
bottle,  test-tube  or  beaker,  without  cracking  the  sur- 
rounding glass.  Take  a  triangular  file  [an  old  one  will 
do],  break  off  its  tip  so  that  a  jagged  point  is  made. 
Keep  this  point  constantly  wet  with  vaseline  or  some  other 
greasy  substance,  and  with  a  circular  grinding  motion 
of  the  arm  and  hand,  bore  into  the  glass.  As  the  file 
point  gets  blunted  break  off  farther  down.  Do  not 
apply  much  pressure  in  the  case  of  beakers  and  thin 
glass,  but  considerable  in  the  case  of  stout  bottles. 


232  MANIPULATIONS. 

When  once  the  file  has  gone  through,  take  a  rat-tail 
file  and,  at  first  cautiously,  file  the  hole  to  the  desired 
size.  Do  not  hold  the  glass  in  such  a  position  that  the 
hand  would  be  cut  in  case  there  should  be  a  sudden 
collapse  of  the  article  on  which  you  are  operating. 

*To  Prevent  Mixing  Glass  Stoppers. 

Never  take  the  stopper  from  a  laboratory  bottle  and 
lay  it  on  the  desk.  Always  take  it  out  by  means  of 
the  middle  finger  and  the  forefinger  with  the  palm 
of  the  hand  held  upward.  This  way  enables  you  to 
hold  the  stopper  [inverted]  between  the  fingers  while 
the  hand  is  free  to  lift  the  bottle  and  pour  its  con- 
tents. Stoppers  left  on  the  desk  get  contaminated  and 
mixed. 

To  Hold  Hot  Beakers,  Test-Tubes,  etc. 

A  beaker  of  boiling  water  may  be  lifted  from  the 
fire  if  the  fingers  grasp  it  by  the  rim  only.  A  piece  of 
paper,  folded  into  a  band  15-20cm  long  and  about  lcm 
wide,  passed  around  the  neck  of  the  test-tube  so  that 
the  fingers  may  grasp  the  two  ends  of  the  paper,  forms 
as  convenient  a  holder  for  a  test-tube  in  which  you  are 
boiling  a  liquid  as  any  of  the  fancy  ones  you  can  buy. 

To  Use  the  Pneumatic  Trough. 

Note.  A  small  iron  sink  can  well  be  converted  into 
a  pneumatic  trough  in  the  manner  described  in  Appendix 
P.  Every  pneumatic  trough  should  have  a  "  bridge." 
The  bridge  recommended  for  the  sink  [Appendix  P] 
will  do  for  any  trough. 


MANIPULATIONS.  233 

For  most  purposes  the  trough  should  be  filled  with 
cold  water.  For  collecting  gases  that  are  soluble  in 
cold  water,  e.g.,  laughing  gas,  hot  water  serves  well. 
In  those  cases  in  which  it  is  desired  to  collect  gases 
free  from  water  vapor,  mercury  is  generally  the  best 
liquid  to  use  in  the  trough.  In  fact  mercury  is  an 
excellent  substance  to  use  at  almost  all  times,  and  it  is 
unfortunate  that  its  cost  prevents  its  more  general  use. 
As  mercury  amalgamates  with  zinc  an  iron  [or  porce- 
lain] trough  is  to  be  preferred  to  one  of  zinc. 

When  a  gas  is  to  be  collected  by  means  of  the 
pneumatic  trough,  the  liquid  in  the  trough  should 
reach  well  above  the  bridge  ;  the  end  of  the  delivery 
tube  should  be  directly  under  the  hole  in  the  bridge  ; 
and  the  receiving  vessel,  inverted  and  filled  with  the 
liquid  of  the  trough,  should  stand  on  the  bridge  directly 
over  the  hole. 

To  Use  Filter  Papers. 

The  filter  paper  should  be  cut  in  circular  form.  For 
most  purposes  the  paper  should  be  folded  together  so 
as  to  halve  its  surface;  then  it  should  again  be  folded 
together,  thus  quartering  it;  finally,  it  should  be  opened 
in  such  a  manner  that  three  of  the  quarters  are  together 
and  form  one  half  of  the  sides  of  a  cone,  while  the 
fourth  quarter  forms  the  other  half.  In  fitting  the 
filter  to  the  funnel,  the  tip  of  the  cone  should  be 
inserted  in  the  point  of  the  funnel,  and  the  paper 
slightly  wet  by  means  of  the  wash-bottle  [unless  water 
would  harm  the  substance  to  be  filtered].  In  general, 
the  filter  paper  should  be  of  such  diameter  that  it  does 


234  MANIPULATIONS. 

not  reach,  when  in  place,  quite  as  high  as  the  edge  of 
the  funnel. 

For  substances  that  filter  slowly  a  plaited  filter  is 
useful.  To  make  a  plaited  filter :  fold  to  quarters,  as 
in  the  case  of  the  common  filter;  then  open  to  a  half 
filter;  the  half  will  show  a  fold  dividing  it  in  halves; 
divide  each  of  these  halves  in  halves  by  a  similar  fold. 
Again  open  out  to  a  half  filter.  Be  sure  that  the  three 
creases  which  divide  the  half  filter  into  quarters  are  all 
alike,  i.e.,  all  have  their  ridges  on  one  side  and  hollows 
on  the  opposite.  Next  make  a  series  of  creases  down 
the  middle  of  each  slice,  taking  care  to  have  these 
latter  creases  point  exactly  opposite  from  the  first.  In 
making  the  creases  be  careful  and  do  not  tear  the  tip  of 
the  cone.  Now  open  the  paper  completely,  and  insert 
it  in  the  funnel  in  such  a  way  that  nowhere  shall  there 
be  two  thicknesses  together.  The  plaits  of  this  funnel 
furnish  a  large  amount  of  surface  for  filtration. 

To  Dry  Bottles,  Flasks,  etc. 

Fit  a  long,  hard  glass  tube  to  the  rubber  tube  from 
the  bellows.  Hold  the  glass  tube  in  the  flame  of  a 
Bunsen  burner  and  force  a  stream  of  hot  air  into  the 
article  that  is  to  be  dried.  Direct  the  stream  of  hot  air 
against  any  drops  of  moisture  that  you  may  see. 

To  Remove  Stoppers  that  have  Stuck. 

First  gently  tap  the  stopper  against  some  rigid  body 
—  as  a  brick  wall  or  iron  beam.  If  this  treatment  fails 
to  start  the  stopper,  immerse  the  bottle,  top  down,  in  a 


MANIPULATIONS.  235 

vessel  of  water.  Allow  the  stopper  to  remain  immersed 
for  several  hours.  If  this  fails  to  start  the  stopper,  wipe 
the  bottle  dry  and  apply  to  its  neck  the  heat  from  the 
small  gas  flame  mentioned  under  "  To  Cut  Glass,"  page 
227.  Turn  the  neck  as  you  apply  the  flame. 

To  Pour  Oases. 

With  a  little  care  gases  may  be  poured  in  a  manner 
similar  to  that  in  which  you  pour  liquids.  Of  course  a 
gas  lighter  than  air  must  be  poured  up  into  an  inverted 
vessel.  In  pouring  a  gas  from  one  tt  to  another  it  is 
well  to  hold  the  fingers  and  hand  around  the  mouths 
of  the  two  tt's  in  a  way  to  protect  the  stream  of 
gas  from  any  current  of  air  that  might  blow  it  to  one 
side. 

To  Use  a  Bunsen  Burner. 

For  almost  all  work  the  Bunsen  burner  should  be 
used  with  its  air- vent  open.  When  this  vent  is  open 
the  air  enters  and  mingles  with  the  gas.  Then  when 
the  gas  issues  from  the  top  of  the  burner  it  burns 
rapidly,  with  a  very  hot  and  almost  colorless  flame. 

If  for  any  reason  you  are  not  using  the  full  supply 
of  gas,  the  supply  of  air  should  be  reduced  to  a  corre- 
sponding amount  by  partly  closing  the  vent. 

Sometimes  a  sudden  gust  of  wind  will  drive  the 
flame  down  the  tube  of  the  Bunsen  burner  and  ignite 
the  gas  as  it  issues  below.  In  this  case  the  burner  is 
said  to  "  snap,"  or  "  strike  back."  A  "  snapped  "  burner 
can  usually  be  detected  by  the  peculiar  color  of  the 
flame  it  shoots  up;  also  by  a  peculiar  odor  which  fills 


236  MANIPULATIONS. 

the  atmosphere  all  around  the  burner.  The  danger 
from  a  "snapped"  burner  is  that  the  base  gets  intensely 
hot  and  is  apt  to  burn  the  fingers.  A  "snapped" 
burner  should  have  its  supply  of  gas  wholly  turned  off 
and  be  re-lighted. 

To  Use  the  Bunsen  Blast-Lamp. 

Allow  the  gas  to  circulate  in  the  outer  chamber,  and 
force  a  current  of  air  in  through  the  small  tube  in  the 
center. 


APPENDICES. 


APPENDICES. 


APPENDIX   A. 

Apparatus    for    the    Electrolytic    Decomposition    of 

Water. 

Prepare  a  vessel  for  holding  water  as  follows  :  Take 
any  common  bottle  of  about  one  quart  capacity.  At  a 
point  about  one-third  down  from  the  neck  to  the 
bottom  cut l  off  the  top  part  parallel  to  the  bottom,  so 
that  the  top  part,  inverted  and  with  a  cork  in  its  neck, 
will  form  a  stout,  shallow  dish.  If  the  neck  is  a  long 
one,  cut  it  off  so  that  not  more  than  one  inch  is  left. 
Fit  a  cork  to  the  neck.  Pass  two  platinum  wires,  each 
about  15cm  long,  between  the  cork  and  the  glass,  well 
up  into  the  body  of  the  vessel.  About  one  inch  of  wire 
should  project  out  from  the  neck.  The  wires  should 
be  as  far  apart  from  one  another  as  possible,'  and  the 
parts  [about  10cm  long]  that  protrude  into  the  vessel 
should  be  twisted  into  spirals.  At  their  lower  ends  the 
platinum  wires  should  be  connected,  by  being  tightly 
twisted,  or,  better,  soldered,  with  copper  wires  leading  to 
two  or  more  Bunsen  cells  or  other  source  of  electricity. 
Support  the  vessel,  with  the  neck  down,  on  a  ring  of 
the  ring  stand.  Light  a  candle,  and,  holding  the  candle 

1  For  cutting  thick  glass,  see  Manipulations. 


240  APPENDICES. 

inverted,  let  the  candle  grease  drop  down  and  fill  the 
neck  of  the  bottle  above  the  cork  while  you  hold  the 
wires  apart  and  keep  their  spirals  well  above  the  grease. 
The  grease  makes  the  joints  water-tight. 

For  the  Bunsen  cell  have  ready  a  two-quart  glass 
battery  jar,  a  porous  cup  as  tall  as  the  battery  jar,  a 
battery  zinc  to  go  around  the  porous  cup,  a  battery 
carbon  to  go  in  the  porous  cup,  two  [one  foot  long] 
pieces  of  copper  wire,  and  two  binding  screws  to  con- 
nect wires  with  the  zinc  and  with  the  carbon.  Fill  the 
jar  nearly  half  full  of  water.  Add  about  one-tenth  as 
much  strong  sulphuric  acid  as  you  have  added  water. 
Add  the  acid  slowly,  with  constant  stirring  with  a  glass 
rod.  Caution :  Sulphuric  acid  is  very  corrosive.  Do 
not  get  any  on  skin  or  clothes.  Put  the  zinc  in  the  jar 
of  acidified  water,  and  let  the  acid  work  for  about  a 
minute.  Invert  the  zinc,  and  let  the  acid  again  act, 
now  on  the  upper  part,  for  about  a  minute.  Then 
remove  the  zinc,  and,  at  the  sink,  with  a  rag  and  a 
little  mercury,  rub  mercury  into  the  zinc,  both  inside 
and  outside  the  cylinder,  till  the  surface  is  bright  and 
well  amalgamated.  Amalgamation  prevents  the  zinc 
from  being  unduly  eaten  away  by  the  acid.  Put  the 
zinc  back,  right  side  up,  in  the  acid.  Put  the  porous 
cup  within  the  zinc.  If  too  much  acid  has  been  put  in 
the  outer  glass  vessel,  now  remove  some.  Fill  the 
porous  cup  about  half  with  nitric  acid,  and  the  other 
half  with  sulphuric  acid,  taking  care  that  the  level  of 
the  acid  in  the  porous  cup  is  the  same  as  that  of  the 
liquid  in  the  glass  vessel  without  the  porous  cup.  Put 
the  carbon  in  the  porous  cup.  By  means  of  tto  binding 


APPENDICES.  241 

screws  and  a  short  piece  of  copper  wire,  connect  the  car- 
bon of  the  cell  with  one  of  the  platinum  wires,  and  con- 
nect the  zinc  with  the  carbon  of  another  cell.  Be  sure 
that  all  points  of  contact  between  the  wires  and  binding 
screws  have  been  freshly  scraped  clean  and  bright. 

Note.  Two  cells  are  necessary.  More  than  two  will 
cause  the  decomposition  of  the  water  to  be  more  rapid, 
and,  consequently,  more  satisfactory. 

Connect  the  zinc  of  the  second  [or  last]  cell  with  the 
other  platinum  wire  of  the  decomposition  apparatus. 


APPENDIX  B. 

Hydrogen  Explosions. 

One  of  the  most  frequent  of  accidents  in  a  laboratory 
for  elementary  chemistry  is  the  explosion  of  a  mixture 
of  hydrogen  and  air.  When  generating  hydrogen  which 
is  to  be  lighted  or  near  which  any  kind  of  fire  is  to 
come,  always  test  its  explosive  qualities,  i.e.,  test  to 
see  whether  air  is  still  mixed  with  the  hydrogen. 

The  test  is  best  made  by  catching  a  small  tt  full  of 
the  gas,  and  [having  removed  the  tt,  while  still  in- 
verted, quickly,  several  feet  from  the  supply  of  hydro- 
gen] touching  a  match  to  the  open  inverted  mouth  of 
the  tube.  A  sharp  ringing  report  shows  danger,  i.e., 
that  there  is  an  explosive  mixture  of  air  and  hydrogen 
present.  Continue  testing  till,  when  the  flame  is  ap- 
plied, there  is  only  a  gentle  pop,  and  the  hydrogen 
burns  quietly  with  a  faint  flame  up  into  the  tt. 


242  APPENDICES. 

A  tt  of  about  lcm  bore,  and  not  more  than  6  or 
8cm  long,  is  the  best  for  this  test.  Such  a  tube  may  be 
made  from  ordinary  large  soft  glass  tube  or  by  cutting 
a  common  small  tt  in  halves.  Hydrogen  explosions 
are  dangerous  from  the  flying  glass  that  is  usually  sent 
in  all  directions.  This  method  of  testing  is  called  "by 
the  explosion  tube." 


APPENDIX  C. 

Test  Papers. 

Note.  The  only  test  papers  that  are  needed  in  ele- 
mentary chemistry  are :  one  to  indicate  an  acid  solution, 
and  one  to  indicate  an  alkaline  solution.  In  preparing 
such  test  papers  use  is  made  of  the  changes  of  color  pro- 
duced by  acids  and  alkalies  on  certain  vegetable  sub- 
stances. Litmus  in  acid  solution  is  red,  and  in  alkaline, 
blue. 

Take  1  part  [e.g.,  10g]  of  the  litmus  of  trade.  Mix 
it  in  a  porcelain  evaporating  dish  with  6  parts  [e.g.,  60g] 
of  water.  Warm  gently,  and  stir  for  about  ten  minutes. 
Filter.  Take  half  the  nitrate,  and,  with  a  glass  rod, 
stir  in  a  drop  or  so  of  very  dilute  sulphuric  acid  [e.g., 
lcc  of  acid  to  50CC  of  water].  Stir  in  acid  till  the  solu- 
tion is  just  turned  red.  Immerse  strips  of  filter  paper 
in  the  red  solution,  keep  the  solution  warm  for  a  little 
while,  remove  the  strips  and  hang  them  on  a  line  [in 
a  room  free  from  ammonia]  to  dry.  They  should  be  of 
a  good  pink  color. 


APPENDICES.  243 

Take  the  remainder  of  the  red  solution  and  add  some 
of  the  blue  [previously  saved  apart],  till  the  color  is 
again  turned  blue.  Immerse  strips  of  paper  in  this 
liquid  and  hang  them  to  dry  in  a  room  free  from  acid 
fumes.  To  detect  an  acid  use  the  blue  paper  ;  to  detect 
an  alkali  use  the  red.  Never  put  a  test  paper  in  any 
solution,  but  always  take  out  a  drop  on  a  glass  rod, 
and  touch  this  drop  to  the  test  paper  held  between  the 
fingers.  Should  the  paper  be  put  in  the  solution,  the 
coloring  matter  would  contaminate  the  solution  itself. 
It  is  never  safe  to  lay  a  test  paper  on  a  desk,  for  the 
desk  itself  may  contaminate  the  test  paper. 

For  detecting  alkaline  substances  papers  treated  with 
turmeric  are  in  some  respects  preferable  to  those  treated 
with  red  litmus.  To  prepare  turmeric  papers,  take  2 
parts  of  water  and  4  of  alcohol  to  1  of  turmeric.  Warm 
gently,  and  stir  for  about  ten  minutes.  Best  warm  the 
alcohol  solution  over  hot  water,  not  over  a  flame,  for 
fear  of  fire.  Filter.  Immerse  strips  of  filter  paper  in 
the  liquid.  Keep  the  papers  in  the  solution  [which 
should  be  kept  warm]  for  a  few  minutes,  and  hang  on 
a  line  to  dry  as  in  the  preparation  of  litmus  paper. 


APPENDIX   D. 
Suction  Pumps. 

Every  laboratory  should  possess  some  form  of  suction 
pump,  both  for  general  use  and,  in  particular,  for  rapid 
nitrations.  The  Bunsen  filter  pump,  though  expensive 
[|7-$10] ,  is  excellent  where  there  is  no  water  pressure 


244  APPENDICES. 

available.  This  pump  is  made  on  the  principle  of  the 
Sprengel  mercury  pump.  Where  water  under  pressure 
can  be  had  any  one  of  the  satisfactory  cheaper  pumps, 
as  the  Richards,  or  the  Fischer  [cost  $l-$3],  may  be 
used. 

For  rapid  filtrations  use  a  stout  glass  bottle  as  a  receiver 
for  the  filtrate.  This  bottle  should  be  fitted  with  a  two- 
hole  rubber  stopper.  Through  one  hole  of  the  stopper 
pass  the  stem  of  the  funnel ;  through  the  second  hole 
pass  a  piece  of  glass  tubing,  which  can  be  connected 
by  a  stout  rubber  hose  with  the  filter  pump.  Make 
[from  a  round  piece  of  platinum  foil  about  one  inch  in 
diameter]  a  little  platinum  cone  to  fit  the  glass  funnel. 
Use  this  cone  to  protect  the  tip  of  the  filter  paper 
when  the  suction  pump  is  used.  In  filtering,  allow  the 
filter  pump  to  exhaust  the  air  from  the  flask.  The  pres- 
sure of  the  atmosphere  then  presses  the  liquid  rapidly 
down  into  the  flask. 


APPENDIX    E. 

Catch-Bottles. 

It  frequently  becomes  necessary  to  "wash,"  or  purify, 
a  gas.  For  this  purpose  the  gas  is  made  to  pass  through 
water,  sulphuric  acid,  or  some  other  liquid,  contained 
in  a  "  catch-bottle."  As  it  is  usually  necessary  to  dry 
the  gas  after  it  has  been  washed,  it  is  well  to  have  on 
hand  two  catch-bottles  connected  and  arranged  so  that 
at  a  moment's  notice  the  wash-liquid  may  be  put  in 
one  and  sulphuric  acid  in  the  other. 


APPENDICES.  245 

Take  two  2-oz.  saltmouth  bottles.  Fit  each  with  a 
good  two-hole  cork,  or,  better,  with  a  two-hole  rubber 
stopper.  Pass  a  glass  tube  through  one  hole  of  the 
stopper  of  the  first  bottle  down  to  the  very  bottom. 
This  tube  should  be  bent  at  a  right  angle  just  above 
the  cork,  and  to  it  should  be  attached  the  tube  that  is 
delivering  the  gas  which  is  to  be  purified.  Through 
the  second  hole  of  this  first  bottle  pass  another  glass 
tube,  beginning  just  at  the  lower  surface  of  the  stopper 
and  extending  over  to  the  second  bottle  and  passing 
through  one  hole  of  the  stopper  of  the  latter  and  down 
to  the  very  bottom.  The  two  bottles  need  not  stand 
more  than  an  inch  or  two  from  each  other.  Through 
the  second  hole  in  the  stopper  to  the  second  bottle  pass 
another  short  piece  of  glass  tube  [bent  at  a  right  angle] 
just  through  the  stopper.  This  last  is  the  exit  tube 
for  the  gas  after  it  has  been  washed  and  dried. 

Put  -the  wash-liquid  in  the  first  bottle,  and  fill  the 
second  about  half  full  of  sulphuric  acid.  After  the  gas 

-L  O 

has  come  in  through  the  first  tube  of  the  first  bottle 
it  should  pass  down  under  the  liquid  and  bubble  up ; 
then  it  should  pass  through  the  tube  to  the  second 
bottle,  where  it  should  bubble  up  through  the  sulphuric 
acid  and  pass  out  through  the  short  exit  tube.  Be  sure 
all  tubes  are  arranged  properly,  and  that  all  joints  are 
tight  before  you  pass  any  gas  through  the  bottles. 


246  APPENDICES. 


APPENDIX    F. 

Generator  for  Gases. 

Take  a  common  narrow-necked  bottle  of  8  to  10-oz. 
capacity.  Bore l  one  or  two  holes  of  4  or  5mm  diameter 
in  the  bottom  of  the  bottle.  Fit  the  bottle  with  a  good 
cork  [better,  a  one-hole  rubber  stopper]  and  a  short  glass 
delivery  tube  bent  at  a  right  angle  and  ending  in  a 
short  piece  of  rubber  tube  carrying  a  screw  pinch-cock, 
by  which  the  flow  of  the  gas  may  be  regulated.  Put  a 
layer  of  broken  glass  about  one  inch  deep  in  the  bottom 
of  the  bottle,  and  set  the  bottle  itself  in  a  large  beaker 
[or,  better,  in  a  battery  jar,  or  in  a  vessel  made  from  a 
large  bottle  whose  top  part  has  been  cut  off]. 

To  Generate  Kon-Combustible  Oxide  of  Carbon. 
Put  small  lumps  of  hard  marble  in  the  generator. 
Insert  the  stopper,  close  the  pinch-cock,  and  pour 
common  muriatic  acid  in  the  outer  vessel  till  the 
surface  of  the  liquid  approaches  within  about  one 
inch  of  the  top  edge.  Open  the  pinch-cock  and  the 
acid  will  force  its  way  into  the  bottle  and  act  on  the 
marble.  When  the  pinch-cock  is  closed  the  accumulat- 
ing gas  forces  the  acid  down  and  out,  and  the  action 
ceases.  The  broken  glass  serves  for  draining  the 
marble,  and  causes  the  action  to  cease  more  promptly 
than  it  would  were  the  marble  placed  on  the  bottom. 
After  the  gas  has  been  generated  it  should  be  washed 
and  dried  by  being  passed  through  two  catch-bottles, 
the  first  of  which  contains  water  and  the  second  sul- 
1  See  Manipulations. 


APPENDICES.  247 

phuric  acid.  The  water  serves  to  stop  the  passage 
of  any  hydrochloric  acid  that  may  be  driven  over, 
and  the  sulphuric  acid  removes  the  water  with  which 
the  gas  at  first  is  always  charged. 

To  Generate  Hydrogen  Sulphide.  Put  sulphide  of 
iron  instead  of  marble  in  the  generator.  The  sulphide 
should  be  broken  in  small  pieces.  Sulphuric  acid  some- 
what diluted  [five  volumes  of  water  to  two  volumes  of 
acid]  may  be  used  with  advantage  in  the  outer  vessel. 

To  Generate  Hydrogen.  Put  zinc  in  the  generator, 
and  dilute  sulphuric  acid  [five  volumes  of  water  to 
one  of  acid]  in  the  outer  vessel. 


APPENDIX    G. 
Hood. 

There  should  be  in  the  laboratory  a  small  closet 
provided  with  a  flue  leading  up  some  chimney  or  into 
the  open  air.  This  closet  should  have  a  glass  window 
that  can  be  opened  and  closed  so  that  articles  put 
"under  the  hood"  can  be  shut  off  from  the  main 
room.  It  is  well,  when  possible,  to  have  an  artificial 
draught  produced  by  a  steam  coil,  burning  gas  jet,  or 
the  like;  also  to  have  gas,  water,  and  a  sink  under 
the  hood. 

APPENDIX   H. 
Preparation  of  Chlorine. 

Fill  a  small  flask  about  one  quarter  with  small  lumps 
of  black  oxide  of  manganese.  Add  common  muriatic 


248  APPENDICES. 

acid  till  the  liquid  and  the  black  oxide  together  fill 
about  one  half  of  the  flask.  Insert  a  one-hole  cork 
and  delivery  tube.  Set  the  flask  with  its  charge  in 
a  beaker,  or  a  pot,  of  water.  Heat  the  water,  and 
chlorine  gas  will  pass  off.  The  delivery  tube  should 
be  connected  with  two  catch-bottles,1  the  first  contain- 
ing water,  the  second  sulphuric  acid.  The  first  catch- 
bottle  serves  to  catch  any  hydrochloric  acid  that  is 
carried  over,  and  the  second  to  dry  the  chlorine. 


APPENDIX  I. 
Sodium  Amalgam. 

For  the  preparation  of  sodium  amalgam  on  the  large 
scale,  have  ready  a  large  Hessian  crucible  capable  of 
holding  at  least  ten  times  as  much  amalgam  as  it  is 
your  intention  to  make.  Put  the  mercury  in  the 
,crucible,  and  heat  with  a  Bunsen  burner.  Take  the 
temperature  of  the  mercury  by  means  of  a  thermometer. 
Have  ready  one  tenth,  by  weight,  as  much  sodium  as 
there  is  mercury.  The  sodium  should  be  in  a  single 
piece.  When  the  temperature  of  the  mercury  has 
-reached  200°  remove  the  burner,  drop  the  sodium  in 
•the  hot  mercury,  cover  the  crucible  with  an  iron  plate, 
or  with  the  bottom  of  some  old  iron  pan,  and  at  once 
step  back.  The  union  takes  place  with  considerable 
commotion.  Before  the  molten  amalgam  has  time  to 
solidify,  pour  it  out  in  a  thin  layer  on  some  smooth 
surface  that  will  not  be  harmed  by  the  heat.  Just  as 
soon  as  the  amalgam  is  cool  enough  to  handle,  break 
1  See  Appendix  E. 


APPENDICES.  249 

it  in  small  pieces,  and  store  it  in  a  tightly-stoppered 
bottle  that  the  air  may  not  give  it  a  troublesome  coat- 
ing of  hydroxide. 

Amalgam  that  has  been  spoiled  by  standing  long  in 
the  air  should  not  be  thrown  away,  but  should  be 
treated  with  water  that  the  mercury  may  be  recovered. 


APPENDIX    J. 
Test  Solutions. 

Caution!  Do  not  get  any  of  either  solution  [1]  or 
solution  [2]  in  the  mouth. 

[1]   Preparation  of  an  Arsenical  Solution  for  Testing. 

Weigh  out  exactly  0.01g  of  the  white  oxide  of  arsenic, 
put  this  in  a  250CC  flask,  add  250CC  of  water  and  about  a 
gram  of  sodium  hydroxide,  and  shake  till  solution  takes 
place.  Use  only  a  single  cc  of  this  solution  at  a  time, 
as  the  test  is  a  very  delicate  one,  and  the  arsenide  of 
hydrogen  formed  is  a  most  terrible  and  deadly  poison. 

In  adding  the  solution  through  the  funnel-tube  care 
should  be  taken  to  let  the  solution  trickle  down  the 
tube  in  such  a  way  that  no  air  is  carried  into  the  bottle. 
Why  avoid  letting  air  enter? 

[2]   Preparation  of  an  Antimonial  Solution  for  Testing. 

Weigh  out  0.03g  of  tartar  emetic  [a  compound  which 
contains  about  40%  of  antimony].  Dissolve  in  250CC 
of  water  and  use  one  cc  at  a  time,  as  in  the  case  of  the 
arsenical  solution. 

Caution !  Do  not  get  any  of  either  of  these  solutions 
in  the  mouth. 


250  APPENDICES. 

APPENDIX  K. 
Use  of  the  Mouth  Blow-Pipe. 

Rest  the  smaller  end  of  the  blow-pipe  on  the  edge  of 
the  Bunsen  burner's  top,  and  blow  directly  through  the 
flame.  The  gas  will  be  carried  along  with  the  blast, 
and  a  slender  cone  of  blue  flame  will  be  projected  at  a 
right  angle  to  the  original  direction  of  the  flame.  If 
the  blast  is  not  powerful  enough  to  use  all  the  gas, 
turn  off  the  supply  of  gas  somewhat.  This  blast  flame, 
though  small,  will  be  found  to  be  intensely  hot.  By 
tipping  the  Bunsen  burner  you  can  direct  the  flame  in 
any  direction. 

In  using  the  blow-pipe,  make  a  reservoir  of  your 
mouth,  while  you  breathe  entirely  through  the  nose. 
With  a  little  experience  you  will  be  able  to  blow  so 
steadily  that  the  small  flame  will  show  little  or  no 
fluctuation  for  minutes  at  a  time. 

When  it  is  desired  to  oxidize  a  substance  care  should 
be  taken  that  only  the  outer  part  of  the  blast  flame 
touches  the  substance.  The  inner  part  of  the  flame 
is  made  up  largely  of  unconsumed  gas  which,  in  its 
eagerness  to  get  oxygen,  acts  as  a  reducer.  Hence 
the  inner  part  of  the  flame  is  often  used  to  bring 
about  reductions  on  a  small  scale. 


APPENDIX    L. 
Arsenical  and  Antimonial  Papers  for  Testing1. 

For  the  arsenical  paper  it  is  best,  when  possible,  to 
get  a  piece  of  wall  paper  that   is   known  to  contain 


APPENDICES.  251 

arsenic.  If  this  cannot  be  found,  take  a  piece  of 
filter  paper,  and  dip  it  in  an  arsenical  solution  made 
five  times  as  strong  as  that  of  Appendix  J  [1].  Hang 
on  a  line  to  dry.  Caution!  Do  not  get  poisoned. 

The  paper  poisoned  with  antimony  may  be  made  by 
dipping  a  piece  of  filter  paper  in  a  solution  five  times 
as  strong  as  that  of  Appendix  J  [2]. 


APPENDIX  M. 
To  Dry  Precipitates. 

Have  ready  a  clean  porcelain  evaporating  dish.  Set 
this  dish  on  gauze  above  the  flame  of  a  Bunsen  burner 
that  has  been  turned  down  to  only  one  fourth  of  its 
ordinary  size.  Carefully  remove  the  precipitate,  paper 
and  all,  from  the  funnel,  and  place  it  in  the  evaporat- 
ing dish.  Watch  the  filter  paper,  and  if  it  shows  the 
least  sign  of  charring,  turn  the  flame  still  lower. 

If  you  are  in  no  hurry,  a  good  way  is  to  leave  the 
precipitate  in  the  funnel  and  set  funnel  and  all  into 
a  ring  supported  just  above  an  iron  plate  which  is 
heated  by  the  Bunsen  burner. 

Excellent  little  ovens  are  sold  for  the  purpose  of 
drying  precipitates  and  the  like,  but  these  are  some- 
what expensive. 

APPENDIX  N. 
To  Nurse  a  Crystal. 

After  a  first  crystallization  has  taken  place,  select 
the  best  formed  crystal,  remove  it  from  the  "mother 


252  APPENDICES. 

liquor "  [as  the  liquid  in  which  the  crystals  were 
formed  is  called],  and  set  it  aside  on  a  bit  of  filter 
paper.  Then  dissolve  the  rest  of  the  crystals,  by 
heat,  in  the  mother  liquor,  and  add  a  little  more 
water.  Filter,  if  dirty.  Cool  the  solution.  Immerse 
the  reserved  crystal  in  the  solution,  and  set  aside  till 
another  deposit  forms.  Much  of  this  second  deposit 
will  take  place  on  the  large  crystal  which  is  thus  made 
to  grow  at  the  expense  of  the  smaller.  Again  remove 
the  large  crystal,  and  repeat  the  process.  Repeat  as 
many  times  as  desired. 

It  is  well,  in  the  beginning,  to  save  two  or  three  crystals 
and  nurse  them  together,  as  nursing  is  apt  to  distort 
a  crystal,  particularly  when  the  crystal  lies  each  time 
on  the  same  face.  Hence,  it  is  well,  also,  to  turn  the 
crystal  occasionally.  If  you  start  with  two  or  three 
crystals,  you  improve  your  chances  of  getting  a  single 
good  one  in  the  end.  Of  course,  any  crystal  that  has 
become  badly  distorted  best  be  dissolved,  that  it  may 
furnish  material  for  the  growth  of  others. 


APPENDIX    0. 
Distilled  Water. 

There  are  but  few  experiments  in  this  book  that 
demand  the  use  of  distilled  water.  For  those  few  the 
water  may  be  purchased  from  the  nearest  apothecary 
shop,  or  it  may  be  distilled  by  the  student,  as  follows  : 
Take  a  glass  retort  [or  a  "boiling  flask"]  and  fill  it 
half  or  two  thirds  with  water  from  the  tap.  Any  retort 


APPENDICES.  253 

that  holds  250-500CC,  or  even  the  wash-bottle  flask  fitted 
with  a  one-hole  cork  and  delivery  tube  will  do.  Support 
the  retort  on  a  stand  in  such  a  way  that  the  water 
may  be  heated  by  the  Bunsen  burner.  Heat  the  water 
rapidly  till  it  boils.  Keep  it  boiling  gently.  The  steam 
that  passes  down  the  neck  of  the  retort  will  be  con- 
densed and  drip  down  in  drops  of  nearly  pure  water, 
while  the  greater  part  of  the  impurities  will  be  left 
behind  in  the  retort.  If  a  boiling  flask  is  used,  it  is 
best  to  pass  the  steam  on  through  a  piece  of  glass  tube 
in  order  that  more  may  be  cooled  and  condensed.  Do 
not  boil  off  more  than  three  quarters  of  the  total  amount 
of  the  water,  as  there  is  danger  of  impurities  coming 
over  in  the  last  quarter.  It  is  also  well  to  reject  the 
first  quarter  that  distills  over,  as  with  this  come  any 
gases  the  water  may  have  dissolved.  But  there  are  not 
enough  of  these  gases  in  ordinary  water  to  vitiate  the 
result  of  any  experiment  in  this  book. 

Store  your  distilled  water  in  a  clean,  well-stoppered 
bottle. 

When  the  laboratory  is  heated  by  steam  it  is  advis- 
able to  condense  steam  from  the  heating  apparatus  and 
to  use  distilled  water  in  many  other  experiments  besides 
those  in  which  its  use  is  imperative. 

A  coil  of  small-bore  tin  pipe  set  in  a  water  jacket 
of  sheet  copper  makes  a  good  condenser.  The  tin  pipe 
should  be  connected  at  its  upper  end  with  the  steam 
pipes,  and  its  lower  end  should  project  from  the  copper 
jacket.  The  water  jacket  should  be  so  arranged  that 
a  stream  of  cold  water  may  be  let  in  at  the  bottom  and 
the  warm  water  may  flow  out  at  the  top.  There  should 


254  APPENDICES. 

be  a  stop-cock,  or  valve,  for  the  steam  pipe,  and  one 
for  the  water  supply. 

As  solid  impurities  are  often  carried  into  the  con- 
denser from  the  steam  pipes,  it  is  best  to  let  the  distilled 
water  trickle  through  a  large  funnel  containing  an  ordi- 
nary filter  paper.  Collect  the  water  in  jugs  or  large 
bottles. 

Students  should  keep  their  wash-bottles  filled  with 
distilled  water  when  the  supply  is  abundant. 


APPENDIX    P. 
Directions  for  a  Student  who  has  no  Instructor. 

It  is  necessary,  of  course,  to  have  a  working  room 
that  you  can  call  your  laboratory.  It  is  not  essential 
that  this  room  be  large  and  built  specially  for  your  work. 
Almost  any  room  will  do,  provided  it  can  be  fitted  with 
a  table,  a  sink,  and  gas  or  gasolene.1 

Do  not  think  that  it  is  necessary  to  have  a  fully- 
equipped  laboratory  before  you  can  commence  to  study 
chemistry.  Get  enough  apparatus  to  start  with,  and 
begin  your  work.  You  will  soon  see  what  you  need, 
and  how  best  to  supply  your  wants.  If  you  get  into 
difficulty,  try  to  think  your  way  out  of  it.  Never  for- 

1  If  it  is  necessary  for  you  to  use  gasolene,  you  should  be  sure  that 
you  state  this  fact  to  your  dealer  in  apparatus,  and  have  burners  suit- 
able for  this  fuel  sent  you.  If  you  have  neither  gas  nor  gasolene,  get 
the  largest  and  best  alcohol  lamp  obtainable  ;  but  even  with  the  best 
alcohol  burners  you  may  have  to  omit  a  number  of  experiments. 
Before  resorting  to  the  use  of  alcohol,  you  should  do  your  best  to 
obtain  gas  or  gasolene. 


APPENDICES.  255 

get  that  there  are  more  ways  than  one  for  attaining 
your  end. 

Your  room  best  have  a  supply  of  water  that  can  be 
turned  on  and  off  by  means  of  a  faucet  at  the  sink. 
If  you  do  not  have  town  or  city  water  delivered  under 
pressure,  the  best  way  is  to  arrange  a  small  tank  above 
your  sink.  The  higher  this  tank  is  above  the  sink  the 
better,  although  two  or  three  feet  will  do  for  almost 
all  work.  A  wooden  box  serves  well  for  the  tank.  Get 
a  plumber  to  line  it  with  zinc  or  copper,  and  fit  to  it 
a  piece  of  pipe  [of  any  kind],  terminating  with  a  faucet 
over  your  sink.  If  the  plumber  can  arrange  a  pump 
to  deliver  water  directly  into  your  tank,  so  much  the 
better.  Otherwise  you  must  fill  the  tank  by  pails.  It 
is  well  to  have  a  second  faucet  with  a  small  delivery 
tube  over  which  you  can  slip  a  piece  of  quarter-inch 
rubber  tube.  This  second  faucet  should  be  a  foot  or 
more  above  the  bottom  of  the  sink,  and  is  needed  in  a 
few  cases,  e.g.,  when  the  filter  pump  is  required.  This 
second  faucet,  however,  is  not  absolutely  necessary,  as 
a  good  substitute  may  be  obtained  by  inserting  a  one- 
hole  stopper  in  the  opening  of  the  other  faucet,  and 
fitting  a  short  piece  of  glass  tube  to  the  faucet  by  means 
of  the  cork.  Over  this  glass  tube  can  be  slipped  the 
rubber  tube. 

The  arrangement  for  your  gas  supply  is  most  simple. 
All  that  is  needed  is  a  gas  cock  terminating  in  a  cor- 
rugated nozzle  over  which  may  be  slipped  the  quarter- 
inch  rubber  tube  of  the  Bunsen  burner.  "  Shut-oil's  " 
of  this  kind,  ready  to  be  screwed  into  a  tee  or  an  elbow, 
come  in  trade.  If  your  plumber  does  not  have  any, 


256  APPENDICES. 

get  him  to  fit  the  end  of  your  gas  pipe  with  a  common 
"shut-off,"  or  cock,  to  the  projecting  end  of  which 
has  been  fitted  a  brass  "pillar"  taken  from  a  common 
bat-wing  burner.  The  clay  tip  should  be  removed 
from  the  brass  pillar  before  the  rubber  tube  is  slipped 
on.  It  is  well  to  have  three  of  these  delivery  places 
for  gas,  although  almost  all  experiments  can  be  per- 
formed with  a  single  gas  tap.  The  blast-lamp  does 
not  need  any  larger  supply  of  gas  than  that  furnished 
by  one  of  these  taps.  The  three  taps  may  be  all  close 
together  or  at  a  distance  from  one  another,  as  the 
gas  can  easily  be  conveyed  in  rubber  tubes  wherever 
needed.  It  is,  however,  best  to  have  the  taps  all  so 
near  the  work  table  that,  when  standing  at  your  work, 
you  can  reach  them  and  turn  the  gas  on  or  off.  A 
special  gas  fitting  is  not  absolutely  essential,  as  the 
rubber  tube  for  the  burner  may  be  slipped  on  any 
ordinary  gas  fixture. 

Though  almost  any  kind  of  sink  will  do,  the  best 
form  seems  to  be  a  small  iron  one  about  twenty  inches 
long,  twelve  inches  wide,  and  five  or  six  inches  deep. 
The  outlet  to  the  sink  should  be  at  one  end,  and  best 
be  reamed  out  to  fit  an  overflow  plug  that  may  be 
inserted  in  order  to  convert  the  sink  into  a  pneumatic 
trough.  The  overflow  plug  is  simply  a  piece  of  pipe 
open  at  both  ends,  an  inch  or  so  shorter  than  the  depth 
of  the  sink,  and  tapered  to  fit  the  reaming  of  the  out- 
let to  the  sink.  When  the  plug  is  put  in  the  hole 
and  the  faucet  opened,  the  water  can  rise  in  the  sink 
no  higher  than  the  top  of  the  plug,  for  at  the  top  it 
finds  an  outlet  down  the  plug  into  the  drain.  As  a 


APPENDICES.    >  257 

. 

bridge  for  this  pneumatic  trough,  provide  a  piece  of 
stout  galvanized  sheet-iron  about  two  and  a  half  inches 
wide  and  twelve  inches  long.  In  the  middle  of  this 
strip  of  iron  make  a  circular  hole  about  half  an  inch 
in  diameter.  Then,  at  points  an  inch  and  a  half  from 
each  end  of  the  strip,  bend  the  strip  at  right  angles 
and  form  a  kind  of  platform,  thus :  , — ,  on  which 
bottles,  jars,  etc.,  can  be  placed,  in  order  to  collect 
gases  when  this  iron  bridge  is  set  on  the  bottom  of  the 
sink.  If  you  cannot  use  your  sink  for  a  pneumatic 
trough,  order  a  small  trough  from  the  apparatus  dealer, 
or  make  use  of  a  deep  pan  or,  better,  earthen  dish. 

You  should  also  have  some  shelves  and  a  drawer  or 
two  for  storing  apparatus  and  chemicals. 

There  should  be  an  earthen  slop-jar  for  waste  material. 

Keep  your  taj>le  neat.  Do  not  let  dirty  dishes  collect. 
Have  a  clearing  off  of  apparatus  at  the  end  of  every 
day's  work,  just  as  if  you  were  a  member  of  a  class  in 
a  laboratory  where  strict  rules  for  neatness  and  order 
are  enforced. 


INDEX. 


INDEX. 


Absolute  scale,  145. 
Acids, 

carbonic,  33. 

with  lime  water,  47. 

with  sodium  hydroxide,  54. 
hydriodic,  80. 
hydrobromic,  78. 
hydrochloric, 

preparation,  56,  57. 

solubility,  58. 

with  ammonium  hydroxide, 
71,  108,  131. 

with  marble,  58. 

with  sodium,  59. 

with  sodium  hydroxide,  60. 
hydrofluoric,  81-82. 
muriatic,  58. 
nitric,  64. 

with  ammonium  hydroxide, 
72. 

with  carbon,  66. 

with  copper,  65. 

with  magnesium,  65. 

with  potassium  hydroxide,  67. 
phosphoric,  33. 
sulphuric,  29. 

removal  of  hydrogen  from,  30. 

with  ammonium  hydroxide, 
72. 

with  calcium  hydroxide,  46. 


Acids  —  sulphuric, 

with  iron  sulphide,  40. 

with  magnesium,  43. 

with  marble,  51. 

with    potassium    hydroxide, 

62. 

with  sodium  carbonate,  55. 

with  sodium  hydroxide,  54. 

with  water,  30,  106. 

with  zinc,  37. 

with  zinc  oxide,  38. 
sulphurous,  27. 
Action  of  acids, 

on  aluminum,  99. 

on  gold,  96. 

on  lead,  91. 

on  platinum,  98. 

on  silver,  93. 

on  tin,  90. 
Agricola,  122. 

Aids    for    determining     atomic 
weights, 

I.  Law  of  Gay-Lussac  and  hy- 

pothesis of  Avogadro,  192. 

II.  Law  of  Dulong  and  Petit, 

208-209. 

III.  Law  of  Isomorphism,  211. 

IV.  Periodic  Law,  213. 
Air, 

with  hydrogen,  21-22. 

with  iron,  11. 

with  phosphorus,  13. 


262 


INDEX. 


Air, 

composition  of,  153. 

effect  of  pressure  on,  126-129. 

weight  and  specific  gravity  of, 

141. 
Alchemy, 

period  of,  114-119. 
Alkaline  substances,  53. 
Alloy,  93. 

fusible,  93. 
Alum,  100. 
Aluminum,  99. 

properties,  99. 

oxidation,  99. 

with  acids,  99. 

sulphate,  99. 
j     Amalgam,  55. 
I         gold,  97. 

sodium,  55. 
i     Ammonia,  68. 

fountain,  70. 
Ammonium,  71. 

hydroxide,  71. 

chloride,  71. 

nitrate,  72. 

sulphate,  72. 
Ampere,  180. 
Analysis,  16,  107,  131. 

qualitative,  130-134. 

quantitative,  164-167. 

proximate,  107. 

ultimate,  107. 

of  marble,  50-51. 

of  table  salt,  165. 
Analytical  chemistry,  107. 
Anhydride,  49. 
Antimony,  87. 

properties,  87. 

oxide,  87. 

chloride,  88. 

hydride,  88. 


Antimony, 

solution  for  testing,  249. 
Apparatus, 

for  chemical  work,  xxix. 

for  electrolysis  of  water,  239. 
Aqua,  221. 

ammonia,  70. 

regia,  97. 
Aqueous  vapor, 

effect  on  gas  volume,  174. 
Arabs,  115. 
Aristotle,  112. 

theory  of  the  elements,  112-113. 
Arsenic,  83. 

properties,  83. 

oxide,  83. 

reduction  of  the  oxide,  84. 

hydride,  84. 

mirror,  84,  85. 

detection  of,  85. 

solution  for  testing,  249. 
Arsenide  of  hydrogen,  84. 
Arseniuretted  hydrogen,  84. 
Arsine,  84. 
Assaying,  131. 
Atom,  170. 
Atomic 

theory,  170. 

weights,  171,  177. 

table  of,  216. 
Aurum,  96. 
Avogadro,  180. 

his  hypothesis,  180. 


Barium,  134. 

nitrate,  159. 
Becher,  138. 
Berthollet,  162. 
Bismuth,  89. 

properties,  89. 


INDEX. 


263 


Bismuth, 

nitrate,  89. 

basic  nitrate,  89. 
Black,  140. 
Blank-books,  xxiii. 
Blast-lamp,  236. 
Blow-pipe,  250. 
Boyle,  125. 

law  of,  126. 

tests  of,  132. 

chemical  theory  of,  135. 

period  of,  125-137. 
Bromides, 

hydrogen,  78. 

sodium,  78. 
Bromine,  77. 

properties,  77. 

replaced  by  chlorine,  78. 

will  replace  iodine,  81. 
Buddha,  113. 
Burner, 

alcohol,  254. 

gasolene,  254. 

Bunsen,  235. 

Bunsen  blast,  236. 

C. 

Calcium,  44. 
properties,  44. 
with  water,  45. 
oxide,  44. 

with  water,  45. 
hydroxide,  45. 

with  carbonic  acid,  47. 

with  sulphuric  acid,  46. 
hydrate  [see  hydroxide], 
carbonate,  47. 
chloride,  59. 
fluoride,  81. 
sulphate,  46,  52. 
light,  50. 


Carbon,  14. 
properties,  14. 
with  oxygen,  18. 
oxides, 

non-combustible  or  dioxide, 
19,  35. 

with  calcium  hydroxide,  49. 
with  potassium,  61. 
with  sodium  hydroxide,  55. 
with  water,  33. 
with  zinc,  35. 

combustible    or     monoxide, 
35-36. 
with  red  oxide  of  mercury, 

37. 

action  with  nitric  acid,  66. 
sulphide,  24. 
Carbonates, 
calcium,  47. 
sodium,  54. 

with  sulphuric  acid,  561 
Carbonic  acid,  33. 

with  calcium  hydroxide,  47-49. 
with  sodium  hydroxide,  64. 
Calorie,  204. 
Calorimeter,  204. 
Catch-bottle,  244. 
Cavendish,  141. 
Chalk,  47. 
Changes,  103. 
chemical,  103-104. 
physical,  103. 
analytical,  107. 
metathetical,  109. 
synthetical,  108. 
caused  by  water,  105-103. 
Charcoal,  14. 
Charles, 

law  of,  143. 
Chemeia,  115. 
Chemi,  115. 


264 


INDEX. 


Chemical, 

changes,  103-104. 

symbols,  177,  218. 

formulae,  219. 

equations,  221-223. 

Examination,  89. 

Investigation,  63. 
Chemicals,  xxix. 
Chinese, 

early  chemical  knowledge  of, 

111. 
Chlorate  of  potassium,  16,  25. 

molecular  weight  of,  198. 
Chlorides,  56. 

ammonium,  71. 

antimony,  88. 

calcium,  59. 

gold,  97. 

hydrogen,  56. 

lead,  92. 

potassium,  199,  212. 

sodium,  57. 
Chlorine,  56. 

preparation,  247. 

properties,  56. 

nascent,  97. 

replaces  bromine,  78. 

replaces  iodine,  80. 
Combining  number,  172. 

for  zinc,  172. 
Combustion  products, 

of  a  candle,  157. 
Compound,  12. 
Conservation  of  mass,  157. 

law  of,  157. 
Constant  weight,  26. 
Contents, 

table  of,  xiii. 
Cooke,  190. 
Copper,  41. 

properties,  41. 


Copper, 

oxide,  41. 
reduction  of  the  oxide,  42. 

with  nitric  acid,  65. 

replaces  silver,  94,  95. 
Corks, 

to  render  tight,  230. 
Crith,  178. 
Crystallization, 

water  of,  31,  106. 
Crystal, 

to  nurse  a  crystal,  251. 

D. 

Dalton's 

law,  143-145. 

atomic  theory,  170. 
Death  of  a  metal,  117. 
Decant,  47. 
Definite  proportions  by  volume, 

law  of,  179. 
Definite  proportions  by  weight, 

law  of,  163. 
Deliquescence,  53. 
Density,  142. 
Diagrams, 

to  be  drawn,  32,  56. 
Diamond,  14,  156. 
Displacement, 

catch  by,  25. 
Drying, 

of  bottles,  etc.,  234. 
Dulong  and  Petit,  202. 


Earliest  period,  111-113. 
Efflorescence,  54. 
Egypt,  115. 
Egyptians, 

early  chemical  knowledge  of, 
111. 


INDEX. 


265 


Electrolysis, 

of  water,  19-20,  180. 
Elements, 

list  of  common,  134. 

list  of  all  recognized,  219. 
Empedocles,  113. 
English  system  of  weights  and 

measures,  5. 
Equations, 

chemical,  221-222. 
Etching  of  glass, 

by  hydrofluoric  acid,  82. 
Examination, 

a  chemical,  89. 
Expansion, 

irregular  of  liquids,  184. 

regular  of  gases,  185. 
Explosion, 

air  and  hydrogen,  21,  241. 

tube,  42,  242. 

F. 

Factor,  38. 

Ferric  chloride,  110. 

Filter, 

paper,  233. 

pump,  243. 
Filtrate,  43. 
Fluorides,  81. 

calcium,  81. 

hydrogen,  81. 

etching  of  glass,  82. 
Fluorine,  81. 
Formulae,  219. 
Fusible  alloy,  93. 

G. 

Gas, 

origin  of  the  term,  121. 
illuminating, 

weight  and  specific  gravity 
of,  149. 


Gas, 

sylvestre,  121,  140. 
Gas-retort  carbon,  14. 
Gay-Lussac,  179. 

law  of,  179. 
Geber,  118. 

sulphur-mercury  theory,  118. 
Generator,  246. 
Glass, 

to  bend,  228. 

to  bore,  231. 

to  cut,  226. 

to  draw,  229. 

to  fire-polish,  228. 

to  mark,  226. 

to  pass  through  rubber,  231. 
Glauber,  123. 
Glauber's  salt,  123. 
Gold,  96. 

properties,  96. 

color,  97. 

with  acids,  96. 

chloride,  97. 

amalgam,  97. 
Graphite,  14. 
Gypsum,  46. 


Halogen,  81. 
Hard  water, 
temporarily,  48. 
permanently,  48. 
Heat,  203. 
specific,  202. 
of  iron,  207. 
of  zinc,  205. 
table,  208. 
Historical  periods, 
earliest,  111-113. 
of  Alchemy,  114-119. 


266 


INDEX. 


Historical  periods, 

medical,  120-124. 

of  Boyle,  125-137. 

of  phlogiston,  138-139. 

pneumatic,  140-160. 

modern,  161-217. 
Holder, 

for  test-tubes,  etc.,  232. 
Hood,  247. 

Hydrates  [see  hydroxides]. 
Hydration,  106. 
Hydriodic  acid,  80. 
Hydrobromic  acid,  78. 
Hydrofluoric  acid,  81. 
Hydrochloric  acid,  56. 

preparation,  56,  57. 

properties,  58. 

solubility,  58. 

with  marble,  58. 

with  sodium,  59. 

with  sodium  hydroxide,  60. 
Hydrogen, 

preparation,  20,  30,  37. 

properties,  20-23. 

lightness,  22. 

weight  and  specific  gravity,  148. 

with  air,  22. 

explosions,  21,  241. 

atomic  weight,  178,  193. 

molecular  weight,  193. 

removed  from  sulphuric  acid, 
30,  37. 

arsenide,  84. 

antimonide,  88. 

bromide,  78. 

chloride,  56. 

fluoride,  81. 

sulphide,  39,  40. 

sulphate  [sulphuric  acid]. 

sulphuretted,  41. 

arseniuretted,  84. 


Hydroxides, 
ammonium,  71. 
calcium,  45. 
potassium,  61. 
sodium,  53. 

I. 

Illuminating  gas, 

weight  and  specific  gravity  of, 

149. 

Indestructibility  of  matter,  157. 
Investigation, 

a  chemical,  63. 
Iodides, 

potassium,  80. 

sodium,  211. 
Iodine,  79. 

properties,  79. 

solubility,  79. 

tincture,  79. 

action  on  the  skin,  79. 

action  on  starch,  79. 

replaced,  80,  81. 
Iron,  11. 

properties,  11. 

with  air,  11. 

with  oxygen,  17. 

oxide,  12,  18. 
with  water,  32. 

chloride,  110. 

sulphate,  31. 

sulphide,  39,  135. 
Isomorphism,  211. 

discovered,  211. 

applied,  211-212. 

J. 

Jews, 

early  chemical  knowledge  of, 

111. 
Joints, 

to  render  tight,  231. 


INDEX. 


267 


Kalium,  60. 

King  of  metals,  96. 

Kjeldahl  flask,  16. 


Language, 

of  chemistry,  218. 
Laughing  gas,  72. 
Lavoisier,  153. 
Law  of, 

Boyle,  126. 

Charles  [see  Dalton's]. 

conservation  of  mass,  157. 

Dalton,  143-145. 

definite  proportions, 
by  volume,  179. 
by  weight,  163. 

Dulong  and  Petit,  202. 

Gay-Lussac,  179. 

isomorphism,  211. 

multiple  proportions,  170. 

periods,  214. 

specific  heats,  208-209. 
Lead,  91. 

properties,  91. 

with  acids,  91. 

oxide,  91. 
with  water,  91. 

chloride,  92. 

sulphate,  92. 

tree,  92. 

replaced  by  zinc,  92. 
Libavius, 

first  chemical  text-book,  120. 
Lime, 

light,  50. 

quick,  44. 

slacked  or  slaked,  45. 

water,  47. 
Litmus  papers,  27,  242. 


M. 

Magnesium,  43. 

properties,  43. 

with  nitric  acid,  65. 

with  sulphuric  acid,  43. 

oxide,  43. 

with  water,  43. 

sulphate,  43. 
Manganese,  26. 

black  oxide,  25. 
Marble,  47. 

analysis  of,  50-51. 

with  sulphuric  acid,  51. 

with  hydrochloric  acid,  58. 
Mass, 

conservation  of,  157. 
Matrass,  15,  230. 
Matter, 

indestructibility  of,  157. 
Mayow,  155. 
Measuring,  3. 
Medical  period,  120-124. 
Mendele"eff,  213. 
Mercury,  14. 

properties,  14. 

with  gold,  97. 

with  sodium,  55. 

oxide,  15,  37,  153. 
Metal, 

death  of,  117. 

resurrection  of,  117. 
Metals, 

with  platinum,  98. 

noble,  97. 

Metathesis,  109,  110. 
Metric  system, 

of  measures  and  weights,  3,  5. 
Meyer,  213. 
Microcrith,  178. 
Millicalorie,  204. 


268 


INDEX. 


Mirror, 

arsenic,  84,  85. 
Mitscherlich,  211. 
Mixture, 

and  chemical  compound,  135. 
Modern  period,  161-217. 
Molecular  theory,  180. 
Molecular  weight,  192. 

determined  by  Chemical  Meth- 
od, 197. 

determined  by  Physical  Meth- 
od, 196. 

of  carbon  dioxide,  196. 

of  chlorate  of  potassium,  198. 

of  chloride  of  potassium,  199. 

of  hydrochloric  acid,  201. 

of  hydrogen,  193. 

of  oxygen,  194,  196. 

of  sulphate  of  potassium,  200. 

of  sulphuric  acid,  200. 

of  water,  194. 
Molecules,  176. 

their  size,  189-190. 

their  movements,  188-189. 
Multiple  Proportions, 

law  of,  170. 
Muriatic  acid,  58. 


Nascent  chlorine,  97. 
Natrium,  52. 
Neutral,  54. 
Neutralization,  54. 
Newlands,  213. 
Nickel,  134. 
Nitrates, 

ammonium,  72. 

bismuth,  89. 

potassium,  67. 
Nitre,  63. 


Nitric  acid,  64. 

with  ammonium  hydroxide,  72. 

with  carbon,  66. 

with  copper,  65. 

with  magnesium,  65. 

with  potassium  hydroxide,  67. 
Nitric  oxide,  72. 
Nitrogen,  63. 

discovered,  150. 

properties,  63. 

oxides,  72. 
Nitrous  oxide,  72. 
Noble  metals,  97. 
Note-book,  xxiii. 

method  of  keeping,  xxiv. 
N.  T.  P.,  146. 
Nursing  a  crystal,  251. 


O. 

Oxides, 
arsenic,  83. 

reduction  of,  84. 
antimony,  87. 
calcium,  44. 

with  water,  45. 
carbon, 

monoxide,  35-36. 

oxidation  of,  37. 
dioxide,  19,  35. 

with  lime  water,  49. 
with  potassium,  61. 
with  sodium  hydroxide,  55. 
with  zinc,  35. 
with  water,  33. 
copper,  41. 

reduced  by  hydrogen,  42. 
hydrogen,  22. 
iron,  12,  18. 
lead,  91. 

with  water,  91. 


INDEX. 


269 


Oxides, 

magnesium,  43. 

with  water,  43. 
manganese,  25. 
mercury,  15,  37,  153. 
nitrogen,  72. 
phosphorus,  14. 

with  water,  33. 
potassium,  61. 

with  water,  61. 
silver,  95. 
sodium,  52. 

with  water,  53. 
sulphur,  27. 

gaseous,  27. 
with  water,  27. 

solid,  27-29. 

with  water,  29-30. 
tin,  90. 
zinc,  34. 

with  water,  34. 

with  sulphuric  acid,  38. 
Oxidation,  19,  37. 
Oxygen,  12. 
discovery,  153. 
preparation,  15,  16,  19,  25. 
properties,  15-20. 
with  iron,  12,  17. 
with  phosphorus,  13,  18. 
with  carbon,  18. 
with  sulphur,  25-27. 
atomic  weight,  172,  194. 
molecular  weight,  194,  196. 

P. 

Palissy,  122. 
Paracelsus,  120. 
Paris, 

plaster  of,  46. 
Periodic  law,  214. 
Petit  and  Dulong,  202. 


Phenomenon,  12. 
Philosophers'  stone,  118. 
Phlogiston,  138. 

period  of,  138-139. 
Phoenicians, 

early  chemical  knowledge  of, 

111. 

Phosphoric  acid,  33. 
Phosphorus,  12. 

properties,  12. 

with  air,  13. 

with  oxygen,  18. 

oxide,  14. 
Pipette,  48. 
Plaster  of  Paris,  46. 
Platinum,  98. 

properties,  98. 

with  acids,  98. 

with  metals,  98. 

with  other  chemicals,  98. 

sponge,  28,  98. 
Plumbers'  solder,  92. 
Plumbum,  91. 
Pneumatic  period,  140-160. 
Potassium,  60. 

properties,  61. 

with  air,  61. 

with  water,  61. 

with  dioxide  of  carbon,  61. 

oxide,  61. 
with  water,  61. 

chlorate,  16,  25,  198. 

chloride,  199,  212. 

hydroxide,  61. 
with  wa'ter,  61. 
with  nitric  acid,  67. 

iodide,  80. 

nitrate,  67. 

sulphate,  62. 
Precipitate,  43. 

to  dry,  251. 


270 


INDEX. 


Pressure, 

effect  on  air,  126-129. 
Priestly,  150. 
Product,  38. 
Proportions, 

multiple,  law  of,  170. 

by  volume,  law  of,  179-180. 

by  weight,  law  of,  163. 
Proust,  162,  168. 
Prout,  175. 

Proximate  analysis,  107. 
Pump, 

air,  142. 

filter,  243-244. 

Q 

Qualitative  analysis,  131. 
Qualitative  tests,  132. 
Quantitative  analysis,  164. 
Quick  lime,  44. 


Reaction,  43. 
Reduction,  36. 

of  oxide  of  carbon,  35-36. 

of  oxide  of  copper,  42. 

of  oxide  of  mercury,  15,  37. 

of  chloride  of  silver,  96. 
Resurrection, 

of  a  metal,  117. 
Richards,  216. 
Richter,  161. 
Rubber, 

to  cut,  231. 
Rutherford,  150. 


Sal  soda,  54. 
Salt, 

definition,  67. 

table,  57. 

made,  57,  60. 


S. 


Salt, 

analyzed,  165. 
Scheele,  150. 
Scheele's  green,  152. 
Silver,  93. 
properties,  93. 
oxidation,  93,  95. 
oxide,  95. 
with  acids,  93. 
chloride,  94,  96. 
sulphide,  95. 
replaced  by  copper,  95. 
purification,  95. 
Simple  substance,  12. 
Slaked  lime,  45. 
Solder,  92. 
Soot,  14. 
Sodium,  52. 
properties,  52. 
with  air,  52. 
with  water,  53. 
oxide,  52. 

with  water,  53. 
amalgam,  55. 
to  prepare  on  a  large  scale, 

248. 

bromide,  78. 
carbonate,  54. 

with  sulphuric  acid,  55. 
chloride,  57. 

hydrate  [see  hydroxide], 
hydroxide,  53. 
with  carbonic  acid,  54. 
with  carbonic  dioxide,  55. 
with  hydrochloric  acid,  60. 
with  sulphuric  acid,  54. 
with  hydrochloric  acid,  59. 
Solution,  103-106. 
Spaces, 

between  the  molecules,  182. 
Spain,  115. 


INDEX. 


271 


Specific  gravity,  142. 

of  air,  141. 

of  carbonic  dioxide,  145. 

of  hydrogen,  148. 

of  illuminating  gas,  149. 

of  oxygen,  196. 
Specific  heat,  202. 

of  iron,  207. 

of  zinc,  205. 

table,  208. 
Spencer,  171. 
Sponge, 

platinum,  28,  98. 
Stahl,  138. 
.Stalactite,  48. 
Stalagmite,  48. 
Stannum,  89. 
Starch, 

with  iodine,  79. 
Stibium,  87. 
Stoichiometry,  224. 
Stoppers, 

to  prevent  mixing,  232. 

to  remove  when  stuck,  234. 
Sublimation,  72. 
Substances, 

simple,  12. 

compound,  12. 
Suidas,  115. 
Sulphates, 

aluminum,  99. 

ammonium,  72. 

calcium,  46,  51. 

iron,  31. 

lead,  92. 

magnesium,  43. 

potassium,  62. 

sodium,  55. 

zinc,  38. 
Sulphides, 

carbon,  24. 


Sulphides, 

hydrogen,  39,  40. 

iron,  39,  135. 

silver,  95. 
Sulphur,  23. 

properties,  23. 

modifications,  24. 

oxides,  25,  27. 

with  hydrogen,  39. 

with  iron,  39,  135. 

with  zin<?,  136. 
Sulphuretted  hydrogen,  41. 
Sulphuric  acid,  29. 

removal     of    hydrogen     from, 
30,    37. 

with  ammonium  hydroxide,  72. 

with  calcium  hydroxide,  46. 

with  iron  sulphide,  40. 

with  magnesium,  43. 

with  marble,  51. 

with  potassium  hydroxide,  62. 

with  sodium  carbonate,  55. 

with  sodium  hydroxide,  54. 

with  water,  30,  106. 

with  zinc,  37. 

with  zinc  oxide,  38. 
Sulphurous  acid,  27. 
Symbols, 

Dalton's,  177. 

modern  chemical,  218. 
Synthesis,  50,  108. 

T. 

Temperature,  202. 
Terra  pinguis,  138. 
Test  papers,  242. 
Tests, 

qualitative,  132. 

used  by  Boyle,  132. 

by  chemical  changes,  133. 

by  physical  changes,  132. 


272 


INDEX. 


Time, 

required     in    the    laboratory, 

xxvii. 
Tin,  89. 

properties,  89. 

cry,  90. 

crystalline  structure,  90. 

oxide,  90. 

with  acids,  90. 

salts  of,  90. 

replaced  by  zinc,  91. 

plate,  90. 
Tincture, 

of  iodine,"  79. 

Transference  of  motion,  203. 
Transmutation,  114,  116. 
Turmeric  paper,  242-243. 

U. 

Ultimate  analysis,  107. 

V. 

Valentine,  119. 
Van  Helmont,  120. 

W. 

Wash-bottle,  6. 
Water, 

preparation,  22. 

electrolysis,  19-20,  180. 

with  iron  oxide,  32. 

with  phosphorus  oxide,  33. 

with  carbonic  dioxide,  33. 


Water, 

with  gaseous  oxide  of  sulphur, 
27. 

with  the  second  oxide  of  sul- 
phur, 29-30. 

with  zinc  oxide,  34. 

with  magnesium  oxide,  43. 

with  calcium  oxide,  45. 

with  sodium  oxide,  53. 

with  potassium  oxide,  61. 

with  lead  oxide,  91. 

with  sodium,  53. 

with  potassium,  61. 

with  sulphuric  acid,  30,  106. 

of  crystallization,  31,  106. 

permanently  hard,  48. 

temporarily  hard,  48. 

distilled,  252. 

molecular  weight,  194. 
Water-bath,  26,  185. 
Weighing,  4. 
Weight, 

constant,  26. 

Z. 

Zinc,  34. 
properties,  34. 
oxide,  34. 

with  sulphuric  acid,  38. 
replaces  tin,  91. 
replaces  lead.  92. 
combining  number  for,  172. 
sulphate,  38. 
with  carbonic  dioxide,  35. 


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